Switch to generic visitor pattern.

Triangle.AbstractMachine.Disassembler/src/main/java/Triangle/AbstractMachine/Disassembler.java

@@ -50,62 +50,18 @@ public class Disassembler {
 	 * @param r            the number of the register.
 	 * @param rightbracket the character to print after the register.
 	 */
-	private static void writeR(char leftbracket, int r, char rightbracket) {
+	private static void writeR(char leftbracket, Register r, char rightbracket) {
 
 		System.out.print(leftbracket);
-		switch (r) {
-		case Machine.CBr:
-			System.out.print("CB");
-			break;
-		case Machine.CTr:
-			System.out.print("CT");
-			break;
-		case Machine.PBr:
-			System.out.print("PB");
-			break;
-		case Machine.PTr:
-			System.out.print("PT");
-			break;
-		case Machine.SBr:
-			System.out.print("SB");
-			break;
-		case Machine.STr:
-			System.out.print("ST");
-			break;
-		case Machine.HBr:
-			System.out.print("HB");
-			break;
-		case Machine.HTr:
-			System.out.print("HT");
-			break;
-		case Machine.LBr:
-			System.out.print("LB");
-			break;
-		case Machine.L1r:
-			System.out.print("L1");
-			break;
-		case Machine.L2r:
-			System.out.print("L2");
-			break;
-		case Machine.L3r:
-			System.out.print("L3");
-			break;
-		case Machine.L4r:
-			System.out.print("L4");
-			break;
-		case Machine.L5r:
-			System.out.print("L5");
-			break;
-		case Machine.L6r:
-			System.out.print("L6");
-			break;
-		case Machine.CPr:
-			System.out.print("CP");
-			break;
-		}
+		System.out.print(r.toString());
 		System.out.print(rightbracket);
 	}
 
+	private static void writeR(char leftBracket, int r, char rightBracket) {
+		var register = Register.values()[r];
+		writeR(leftBracket, register, rightBracket);
+	}
+
 	/**
 	 * Writes a void n-field of an instruction.
 	 */
@@ -142,89 +98,90 @@ public class Disassembler {
 	 * @param d the displacment of the primitive routine.
 	 */
 	private static void writePrimitive(int d) {
-		switch (d) {
-		case Machine.idDisplacement:
+		var primitive = Primitive.values()[d];
+		switch (primitive) {
+		case ID:
 			System.out.print("id      ");
 			break;
-		case Machine.notDisplacement:
+		case NOT:
 			System.out.print("not     ");
 			break;
-		case Machine.andDisplacement:
+		case AND:
 			System.out.print("and     ");
 			break;
-		case Machine.orDisplacement:
+		case OR:
 			System.out.print("or      ");
 			break;
-		case Machine.succDisplacement:
+		case SUCC:
 			System.out.print("succ    ");
 			break;
-		case Machine.predDisplacement:
+		case PRED:
 			System.out.print("pred    ");
 			break;
-		case Machine.negDisplacement:
+		case NEG:
 			System.out.print("neg     ");
 			break;
-		case Machine.addDisplacement:
+		case ADD:
 			System.out.print("add     ");
 			break;
-		case Machine.subDisplacement:
+		case SUB:
 			System.out.print("sub     ");
 			break;
-		case Machine.multDisplacement:
+		case MULT:
 			System.out.print("mult    ");
 			break;
-		case Machine.divDisplacement:
+		case DIV:
 			System.out.print("div     ");
 			break;
-		case Machine.modDisplacement:
+		case MOD:
 			System.out.print("mod     ");
 			break;
-		case Machine.ltDisplacement:
+		case LT:
 			System.out.print("lt      ");
 			break;
-		case Machine.leDisplacement:
+		case LE:
 			System.out.print("le      ");
 			break;
-		case Machine.geDisplacement:
+		case GE:
 			System.out.print("ge      ");
 			break;
-		case Machine.gtDisplacement:
+		case GT:
 			System.out.print("gt      ");
 			break;
-		case Machine.eqDisplacement:
+		case EQ:
 			System.out.print("eq      ");
 			break;
-		case Machine.neDisplacement:
+		case NE:
 			System.out.print("ne      ");
 			break;
-		case Machine.eolDisplacement:
+		case EOL:
 			System.out.print("eol     ");
 			break;
-		case Machine.eofDisplacement:
+		case EOF:
 			System.out.print("eof     ");
 			break;
-		case Machine.getDisplacement:
+		case GET:
 			System.out.print("get     ");
 			break;
-		case Machine.putDisplacement:
+		case PUT:
 			System.out.print("put     ");
 			break;
-		case Machine.geteolDisplacement:
+		case GETEOL:
 			System.out.print("geteol  ");
 			break;
-		case Machine.puteolDisplacement:
+		case PUTEOL:
 			System.out.print("puteol  ");
 			break;
-		case Machine.getintDisplacement:
+		case GETINT:
 			System.out.print("getint  ");
 			break;
-		case Machine.putintDisplacement:
+		case PUTINT:
 			System.out.print("putint  ");
 			break;
-		case Machine.newDisplacement:
+		case NEW:
 			System.out.print("new     ");
 			break;
-		case Machine.disposeDisplacement:
+		case DISPOSE:
 			System.out.print("dispose ");
 			break;
 		}
@@ -237,98 +194,98 @@ public class Disassembler {
 	 */
 	private static void writeInstruction(Instruction instr) {
 
-		switch (instr.op) {
-		case Machine.LOADop:
+		switch (instr.opCode) {
+		case LOAD:
 			System.out.print("LOAD  ");
-			writeN(instr.n);
-			writeD(instr.d);
-			writeR('[', instr.r, ']');
+			writeN(instr.length);
+			writeD(instr.operand);
+			writeR('[', instr.register, ']');
 			break;
 
-		case Machine.LOADAop:
+		case LOADA:
 			System.out.print("LOADA ");
 			blankN();
-			writeD(instr.d);
-			writeR('[', instr.r, ']');
+			writeD(instr.operand);
+			writeR('[', instr.register, ']');
 			break;
 
-		case Machine.LOADIop:
+		case LOADI:
 			System.out.print("LOADI ");
-			writeN(instr.n);
+			writeN(instr.length);
 			break;
 
-		case Machine.LOADLop:
+		case LOADL:
 			System.out.print("LOADL ");
 			blankN();
-			writeD(instr.d);
+			writeD(instr.operand);
 			break;
 
-		case Machine.STOREop:
+		case STORE:
 			System.out.print("STORE ");
-			writeN(instr.n);
-			writeD(instr.d);
-			writeR('[', instr.r, ']');
+			writeN(instr.length);
+			writeD(instr.operand);
+			writeR('[', instr.register, ']');
 			break;
 
-		case Machine.STOREIop:
+		case STOREI:
 			System.out.print("STOREI");
-			writeN(instr.n);
+			writeN(instr.length);
 			break;
 
-		case Machine.CALLop:
+		case CALL:
 			System.out.print("CALL  ");
-			if (instr.r == Machine.PBr) {
+			if (instr.register == Register.PB) {
 				blankN();
-				writePrimitive(instr.d);
+				writePrimitive(instr.operand);
 			} else {
-				writeR('(', instr.n, ')');
+				writeR('(', instr.length, ')');
 				System.out.print("  ");
-				writeD(instr.d);
-				writeR('[', instr.r, ']');
+				writeD(instr.operand);
+				writeR('[', instr.register, ']');
 			}
 			break;
 
-		case Machine.CALLIop:
+		case CALLI:
 			System.out.print("CALLI ");
 			break;
 
-		case Machine.RETURNop:
+		case RETURN:
 			System.out.print("RETURN");
-			writeN(instr.n);
-			writeD(instr.d);
+			writeN(instr.length);
+			writeD(instr.operand);
 			break;
 
-		case Machine.PUSHop:
+		case PUSH:
 			System.out.print("PUSH  ");
 			blankN();
-			writeD(instr.d);
+			writeD(instr.operand);
 			break;
 
-		case Machine.POPop:
+		case POP:
 			System.out.print("POP   ");
-			writeN(instr.n);
-			writeD(instr.d);
+			writeN(instr.length);
+			writeD(instr.operand);
 			break;
 
-		case Machine.JUMPop:
+		case JUMP:
 			System.out.print("JUMP  ");
 			blankN();
-			writeD(instr.d);
-			writeR('[', instr.r, ']');
+			writeD(instr.operand);
+			writeR('[', instr.register, ']');
 			break;
 
-		case Machine.JUMPIop:
+		case JUMPI:
 			System.out.print("JUMPI ");
 			break;
 
-		case Machine.JUMPIFop:
+		case JUMPIF:
 			System.out.print("JUMPIF");
-			writeN(instr.n);
-			writeD(instr.d);
-			writeR('[', instr.r, ']');
+			writeN(instr.length);
+			writeD(instr.operand);
+			writeR('[', instr.register, ']');
 			break;
 
-		case Machine.HALTop:
+		case HALT:
 			System.out.print("HALT  ");
 		}
 	}

Triangle.AbstractMachine.Interpreter/src/main/java/Triangle/AbstractMachine/Interpreter.java

@@ -40,41 +40,46 @@ public class Interpreter {
 	static long accumulator;
 
 	static int content(int r) {
+		var register = Register.values()[r];
+		return content(register);
+	}
+
+	static int content(Register r) {
 		// Returns the current content of register r,
 		// even if r is one of the pseudo-registers L1..L6.
 
 		switch (r) {
-		case Machine.CBr:
+		case CB:
 			return CB;
-		case Machine.CTr:
+		case CT:
 			return CT;
-		case Machine.PBr:
+		case PB:
 			return Machine.PB;
-		case Machine.PTr:
+		case PT:
 			return Machine.PT;
-		case Machine.SBr:
+		case SB:
 			return SB;
-		case Machine.STr:
+		case ST:
 			return ST;
-		case Machine.HBr:
+		case HB:
 			return HB;
-		case Machine.HTr:
+		case HT:
 			return HT;
-		case Machine.LBr:
+		case LB:
 			return LB;
-		case Machine.L1r:
+		case L1:
 			return data[LB];
-		case Machine.L2r:
+		case L2:
 			return data[data[LB]];
-		case Machine.L3r:
+		case L3:
 			return data[data[data[LB]]];
-		case Machine.L4r:
+		case L4:
 			return data[data[data[data[LB]]]];
-		case Machine.L5r:
+		case L5:
 			return data[data[data[data[data[LB]]]]];
-		case Machine.L6r:
+		case L6:
 			return data[data[data[data[data[data[LB]]]]]];
-		case Machine.CPr:
+		case CP:
 			return CP;
 		default:
 			return 0;
@@ -85,7 +90,6 @@ public class Interpreter {
 
 	static void dump() {
 		// Writes a summary of the machine state.
-		int addr, staticLink, dynamicLink, localRegNum;
 
 		System.out.println("");
 		System.out.println("State of data store and registers:");
@@ -95,7 +99,7 @@ public class Interpreter {
 		else {
 			System.out.println("       HB-->");
 			System.out.println("            |--------|");
-			for (addr = HB - 1; addr >= HT; addr--) {
+			for (var addr = HB - 1; addr >= HT; addr--) {
 				System.out.print(addr + ":");
 				if (addr == HT)
 					System.out.print(" HT-->");
@@ -110,41 +114,43 @@ public class Interpreter {
 		if (ST == SB)
 			System.out.println("            |--------|          (stack is empty)");
 		else {
-			dynamicLink = LB;
-			staticLink = LB;
-			localRegNum = Machine.LBr;
+			var dynamicLink = LB;
+			var staticLink = LB;
+			var localRegNum = Register.LB;
 			System.out.println("      ST--> |////////|");
 			System.out.println("            |--------|");
-			for (addr = ST - 1; addr >= SB; addr--) {
+			for (var addr = ST - 1; addr >= SB; addr--) {
 				System.out.print(addr + ":");
 				if (addr == SB)
 					System.out.print(" SB-->");
 				else if (addr == staticLink) {
 					switch (localRegNum) {
-					case Machine.LBr:
+					case LB:
 						System.out.print(" LB-->");
 						break;
-					case Machine.L1r:
+					case L1:
 						System.out.print(" L1-->");
 						break;
-					case Machine.L2r:
+					case L2:
 						System.out.print(" L2-->");
 						break;
-					case Machine.L3r:
+					case L3:
 						System.out.print(" L3-->");
 						break;
-					case Machine.L4r:
+					case L4:
 						System.out.print(" L4-->");
 						break;
-					case Machine.L5r:
+					case L5:
 						System.out.print(" L5-->");
 						break;
-					case Machine.L6r:
+					case L6:
 						System.out.print(" L6-->");
 						break;
+					default:
+						break;
 					}
 					staticLink = data[addr];
-					localRegNum = localRegNum + 1;
+					localRegNum = Register.values()[localRegNum.ordinal() + 1];
 				} else
 					System.out.print("      ");
 				if ((addr == dynamicLink) && (dynamicLink != SB))
@@ -277,45 +283,46 @@ public class Interpreter {
 		int addr, size;
 		char ch;
 
-		switch (primitiveDisplacement) {
-		case Machine.idDisplacement:
+		var primitive = Primitive.values()[primitiveDisplacement];
+		switch (primitive) {
+		case ID:
 			break; // nothing to be done
-		case Machine.notDisplacement:
+		case NOT:
 			data[ST - 1] = toInt(!isTrue(data[ST - 1]));
 			break;
-		case Machine.andDisplacement:
+		case AND:
 			ST = ST - 1;
 			data[ST - 1] = toInt(isTrue(data[ST - 1]) & isTrue(data[ST]));
 			break;
-		case Machine.orDisplacement:
+		case OR:
 			ST = ST - 1;
 			data[ST - 1] = toInt(isTrue(data[ST - 1]) | isTrue(data[ST]));
 			break;
-		case Machine.succDisplacement:
+		case SUCC:
 			data[ST - 1] = overflowChecked(data[ST - 1] + 1);
 			break;
-		case Machine.predDisplacement:
+		case PRED:
 			data[ST - 1] = overflowChecked(data[ST - 1] - 1);
 			break;
-		case Machine.negDisplacement:
+		case NEG:
 			data[ST - 1] = -data[ST - 1];
 			break;
-		case Machine.addDisplacement:
+		case ADD:
 			ST = ST - 1;
 			accumulator = data[ST - 1];
 			data[ST - 1] = overflowChecked(accumulator + data[ST]);
 			break;
-		case Machine.subDisplacement:
+		case SUB:
 			ST = ST - 1;
 			accumulator = data[ST - 1];
 			data[ST - 1] = overflowChecked(accumulator - data[ST]);
 			break;
-		case Machine.multDisplacement:
+		case MULT:
 			ST = ST - 1;
 			accumulator = data[ST - 1];
 			data[ST - 1] = overflowChecked(accumulator * data[ST]);
 			break;
-		case Machine.divDisplacement:
+		case DIV:
 			ST = ST - 1;
 			accumulator = data[ST - 1];
 			if (data[ST] != 0)
@@ -323,7 +330,7 @@ public class Interpreter {
 			else
 				status = failedZeroDivide;
 			break;
-		case Machine.modDisplacement:
+		case MOD:
 			ST = ST - 1;
 			accumulator = data[ST - 1];
 			if (data[ST] != 0)
@@ -331,41 +338,41 @@ public class Interpreter {
 			else
 				status = failedZeroDivide;
 			break;
-		case Machine.ltDisplacement:
+		case LT:
 			ST = ST - 1;
 			data[ST - 1] = toInt(data[ST - 1] < data[ST]);
 			break;
-		case Machine.leDisplacement:
+		case LE:
 			ST = ST - 1;
 			data[ST - 1] = toInt(data[ST - 1] <= data[ST]);
 			break;
-		case Machine.geDisplacement:
+		case GE:
 			ST = ST - 1;
 			data[ST - 1] = toInt(data[ST - 1] >= data[ST]);
 			break;
-		case Machine.gtDisplacement:
+		case GT:
 			ST = ST - 1;
 			data[ST - 1] = toInt(data[ST - 1] > data[ST]);
 			break;
-		case Machine.eqDisplacement:
+		case EQ:
 			size = data[ST - 1]; // size of each comparand
 			ST = ST - 2 * size;
 			data[ST - 1] = toInt(equal(size, ST - 1, ST - 1 + size));
 			break;
-		case Machine.neDisplacement:
+		case NE:
 			size = data[ST - 1]; // size of each comparand
 			ST = ST - 2 * size;
 			data[ST - 1] = toInt(!equal(size, ST - 1, ST - 1 + size));
 			break;
-		case Machine.eolDisplacement:
+		case EOL:
 			data[ST] = toInt(currentChar == '\n');
 			ST = ST + 1;
 			break;
-		case Machine.eofDisplacement:
+		case EOF:
 			data[ST] = toInt(currentChar == -1);
 			ST = ST + 1;
 			break;
-		case Machine.getDisplacement:
+		case GET:
 			ST = ST - 1;
 			addr = data[ST];
 			try {
@@ -375,12 +382,12 @@ public class Interpreter {
 			}
 			data[addr] = currentChar;
 			break;
-		case Machine.putDisplacement:
+		case PUT:
 			ST = ST - 1;
 			ch = (char) data[ST];
 			System.out.print(ch);
 			break;
-		case Machine.geteolDisplacement:
+		case GETEOL:
 			try {
 				while ((currentChar = System.in.read()) != '\n')
 					;
@@ -388,10 +395,10 @@ public class Interpreter {
 				status = failedIOError;
 			}
 			break;
-		case Machine.puteolDisplacement:
+		case PUTEOL:
 			System.out.println("");
 			break;
-		case Machine.getintDisplacement:
+		case GETINT:
 			ST = ST - 1;
 			addr = data[ST];
 			try {
@@ -401,18 +408,18 @@ public class Interpreter {
 			}
 			data[addr] = (int) accumulator;
 			break;
-		case Machine.putintDisplacement:
+		case PUTINT:
 			ST = ST - 1;
 			accumulator = data[ST];
 			System.out.print(accumulator);
 			break;
-		case Machine.newDisplacement:
+		case NEW:
 			size = data[ST - 1];
 			checkSpace(size);
 			HT = HT - size;
 			data[ST - 1] = HT;
 			break;
-		case Machine.disposeDisplacement:
+		case DISPOSE:
 			ST = ST - 1; // no action taken at present
 			break;
 		}
@@ -422,7 +429,6 @@ public class Interpreter {
 		// Runs the program in code store.
 
 		Instruction currentInstr;
-		int op, r, n, d, addr, index;
 
 		// Initialize registers ...
 		ST = SB;
@@ -434,65 +440,67 @@ public class Interpreter {
 			// Fetch instruction ...
 			currentInstr = Machine.code[CP];
 			// Decode instruction ...
-			op = currentInstr.op;
-			r = currentInstr.r;
-			n = currentInstr.n;
-			d = currentInstr.d;
+			var op = currentInstr.opCode;
+			var r = currentInstr.register;
+			var n = currentInstr.length;
+			var d = currentInstr.operand;
+			int addr;
+
 			// Execute instruction ...
 			switch (op) {
-			case Machine.LOADop:
+			case LOAD:
 				addr = d + content(r);
 				checkSpace(n);
-				for (index = 0; index < n; index++)
+				for (var index = 0; index < n; index++)
 					data[ST + index] = data[addr + index];
 				ST = ST + n;
 				CP = CP + 1;
 				break;
-			case Machine.LOADAop:
+			case LOADA:
 				addr = d + content(r);
 				checkSpace(1);
 				data[ST] = addr;
 				ST = ST + 1;
 				CP = CP + 1;
 				break;
-			case Machine.LOADIop:
+			case LOADI:
 				ST = ST - 1;
 				addr = data[ST];
 				checkSpace(n);
-				for (index = 0; index < n; index++)
+				for (var index = 0; index < n; index++)
 					data[ST + index] = data[addr + index];
 				ST = ST + n;
 				CP = CP + 1;
 				break;
-			case Machine.LOADLop:
+			case LOADL:
 				checkSpace(1);
 				data[ST] = d;
 				ST = ST + 1;
 				CP = CP + 1;
 				break;
-			case Machine.STOREop:
+			case STORE:
 				addr = d + content(r);
 				ST = ST - n;
-				for (index = 0; index < n; index++)
+				for (var index = 0; index < n; index++)
 					data[addr + index] = data[ST + index];
 				CP = CP + 1;
 				break;
-			case Machine.STOREIop:
+			case STOREI:
 				ST = ST - 1;
 				addr = data[ST];
 				ST = ST - n;
-				for (index = 0; index < n; index++)
+				for (var index = 0; index < n; index++)
 					data[addr + index] = data[ST + index];
 				CP = CP + 1;
 				break;
-			case Machine.CALLop:
+			case CALL:
 				addr = d + content(r);
 				if (addr >= Machine.PB) {
 					callPrimitive(addr - Machine.PB);
 					CP = CP + 1;
 				} else {
 					checkSpace(3);
-					if ((0 <= n) && (n <= 15))
+					if (0 <= n && n <= 15)
 						data[ST] = content(n); // static link
 					else
 						status = failedInvalidInstruction;
@@ -503,7 +511,7 @@ public class Interpreter {
 					CP = addr;
 				}
 				break;
-			case Machine.CALLIop:
+			case CALLI:
 				ST = ST - 2;
 				addr = data[ST + 1];
 				if (addr >= Machine.PB) {
@@ -518,43 +526,43 @@ public class Interpreter {
 					CP = addr;
 				}
 				break;
-			case Machine.RETURNop:
+			case RETURN:
 				addr = LB - d;
 				CP = data[LB + 2];
 				LB = data[LB + 1];
 				ST = ST - n;
-				for (index = 0; index < n; index++)
+				for (var index = 0; index < n; index++)
 					data[addr + index] = data[ST + index];
 				ST = addr + n;
 				break;
-			case Machine.PUSHop:
+			case PUSH:
 				checkSpace(d);
 				ST = ST + d;
 				CP = CP + 1;
 				break;
-			case Machine.POPop:
+			case POP:
 				addr = ST - n - d;
 				ST = ST - n;
-				for (index = 0; index < n; index++)
+				for (var index = 0; index < n; index++)
 					data[addr + index] = data[ST + index];
 				ST = addr + n;
 				CP = CP + 1;
 				break;
-			case Machine.JUMPop:
+			case JUMP:
 				CP = d + content(r);
 				break;
-			case Machine.JUMPIop:
+			case JUMPI:
 				ST = ST - 1;
 				CP = data[ST];
 				break;
-			case Machine.JUMPIFop:
+			case JUMPIF:
 				ST = ST - 1;
 				if (data[ST] == n)
 					CP = d + content(r);
 				else
 					CP = CP + 1;
 				break;
-			case Machine.HALTop:
+			case HALT:
 				status = halted;
 				break;
 			}

Triangle.AbstractMachine/src/main/java/Triangle/AbstractMachine/Instruction.java

@@ -21,13 +21,6 @@ import java.io.IOException;
 
 public class Instruction {
 
-	public Instruction() {
-		op = 0;
-		r = 0;
-		n = 0;
-		d = 0;
-	}
-
 	// Java has no type synonyms, so the following representations are
 	// assumed:
 	//
@@ -37,26 +30,36 @@ public class Instruction {
 	// Operand = -32767..+32767; {16 bits signed}
 
 	// Represents TAM instructions.
-	public int op; // OpCode
-	public int r; // RegisterNumber
-	public int n; // Length
-	public int d; // Operand
+	final OpCode opCode;
+	final Register register;
+	final int length;
+	int operand; // Not final to allow for patching jump address
+
+	public Instruction(OpCode opcode, Register register, int length, int operand) {
+		this.opCode = opcode;
+		this.register = register;
+		this.length = length;
+		this.operand = operand;
+	}
+
+	public void setOperand(int operand) {
+		this.operand = operand;
+	}
 	
 	public void write(DataOutputStream output) throws IOException {
-		output.writeInt(op);
-		output.writeInt(r);
-		output.writeInt(n);
-		output.writeInt(d);
+		output.writeInt(opCode.ordinal());
+		output.writeInt(register.ordinal());
+		output.writeInt(length);
+		output.writeInt(operand);
 	}
 
 	public static Instruction read(DataInputStream input) throws IOException {
-		Instruction inst = new Instruction();
 		try {
-			inst.op = input.readInt();
-			inst.r = input.readInt();
-			inst.n = input.readInt();
-			inst.d = input.readInt();
-			return inst;
+			var opCode = OpCode.values()[input.readInt()];
+			var register = Register.values()[input.readInt()];
+			var length = input.readInt();
+			var operand = input.readInt();
+			return new Instruction(opCode, register, length, operand);
 		} catch (EOFException s) {
 			return null;
 		}

Triangle.AbstractMachine/src/main/java/Triangle/AbstractMachine/Machine.java

@@ -31,10 +31,6 @@ public final class Machine {
 
 	// INSTRUCTIONS
 
-	// Operation codes
-	public final static int LOADop = 0, LOADAop = 1, LOADIop = 2, LOADLop = 3, STOREop = 4, STOREIop = 5, CALLop = 6,
-			CALLIop = 7, RETURNop = 8, PUSHop = 10, POPop = 11, JUMPop = 12, JUMPIop = 13, JUMPIFop = 14, HALTop = 15;
-
 	// CODE STORE
 
 	public static Instruction[] code = new Instruction[1024];
@@ -46,9 +42,6 @@ public final class Machine {
 
 	// REGISTER NUMBERS
 
-	public final static int CBr = 0, CTr = 1, PBr = 2, PTr = 3, SBr = 4, STr = 5, HBr = 6, HTr = 7, LBr = 8,
-			L1r = LBr + 1, L2r = LBr + 2, L3r = LBr + 3, L4r = LBr + 4, L5r = LBr + 5, L6r = LBr + 6, CPr = 15;
-
 	// DATA REPRESENTATION
 
 	public final static int booleanSize = 1, characterSize = 1, integerSize = 1, addressSize = 1,
@@ -58,14 +51,4 @@ public final class Machine {
 
 			falseRep = 0, trueRep = 1, maxintRep = 32767;
 
-	// ADDRESSES OF PRIMITIVE ROUTINES
-
-	public final static int idDisplacement = 1, notDisplacement = 2, andDisplacement = 3, orDisplacement = 4,
-			succDisplacement = 5, predDisplacement = 6, negDisplacement = 7, addDisplacement = 8, subDisplacement = 9,
-			multDisplacement = 10, divDisplacement = 11, modDisplacement = 12, ltDisplacement = 13, leDisplacement = 14,
-			geDisplacement = 15, gtDisplacement = 16, eqDisplacement = 17, neDisplacement = 18, eolDisplacement = 19,
-			eofDisplacement = 20, getDisplacement = 21, putDisplacement = 22, geteolDisplacement = 23,
-			puteolDisplacement = 24, getintDisplacement = 25, putintDisplacement = 26, newDisplacement = 27,
-			disposeDisplacement = 28;
-
 }

Triangle.AbstractMachine/src/main/java/Triangle/AbstractMachine/OpCode.java

@@ -0,0 +1,5 @@
+package Triangle.AbstractMachine;
+
+public enum OpCode {
+	LOAD, LOADA, LOADI, LOADL, STORE, STOREI, CALL, CALLI, RETURN, PUSH, POP, JUMP, JUMPI, JUMPIF, HALT
+}

Triangle.AbstractMachine/src/main/java/Triangle/AbstractMachine/Primitive.java

@@ -0,0 +1,6 @@
+package Triangle.AbstractMachine;
+
+public enum Primitive {
+	ID, NOT, AND, OR, SUCC, PRED, NEG, ADD, SUB, MULT, DIV, MOD, LT, LE, GE, GT, EQ, NE, EOL, EOF, GET, PUT, GETEOL,
+	PUTEOL, GETINT, PUTINT, NEW, DISPOSE
+}

Triangle.AbstractMachine/src/main/java/Triangle/AbstractMachine/Register.java

@@ -0,0 +1,5 @@
+package Triangle.AbstractMachine;
+
+public enum Register {
+	CB, CT, PB, PT, SB, ST, HB, HT, LB, L1, L2, L3, L4, L5, L6, CP
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/AbstractSyntaxTree.java

@@ -14,12 +14,14 @@
 
 package Triangle.AbstractSyntaxTrees;
 
-import Triangle.CodeGenerator.RuntimeEntity;
+import Triangle.CodeGenerator.Entities.RuntimeEntity;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class AST {
+public abstract class AbstractSyntaxTree {
 
-	public AST(SourcePosition position) {
+	private final SourcePosition position;
+
+	public AbstractSyntaxTree(SourcePosition position) {
 		this.position = position;
 		entity = null;
 	}
@@ -28,13 +30,5 @@ public abstract class AST {
 		return position;
 	}
 
-	public abstract Object visit(Visitor v, Object o);
-
-	public final Object visit(Visitor v) {
-		return visit(v, null);
-	}
-	
-	public final SourcePosition position;
-	
 	public RuntimeEntity entity;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/ActualParameter.java

@@ -12,13 +12,21 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class ActualParameter extends AST {
+public abstract class ActualParameter extends AbstractSyntaxTree {
 
 	public ActualParameter(SourcePosition position) {
 		super(position);
 	}
+
+	public abstract <TArg, TResult> TResult visit(ActualParameterVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(ActualParameterVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/ActualParameterSequence.java

@@ -12,13 +12,21 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class ActualParameterSequence extends AST {
+public abstract class ActualParameterSequence extends AbstractSyntaxTree {
 
 	public ActualParameterSequence(SourcePosition position) {
 		super(position);
 	}
+
+	public abstract <TArg, TResult> TResult visit(ActualParameterSequenceVisitor<TArg, TResult> v, TArg arg);
+
+	public <TResult> TResult visit(ActualParameterSequenceVisitor<Void, TResult> v) {
+		return visit(v, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/ConstActualParameter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ConstActualParameter extends ActualParameter {
@@ -23,10 +25,9 @@ public class ConstActualParameter extends ActualParameter {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitConstActualParameter(this, o);
+	public <TArg, TResult> TResult visit(ActualParameterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitConstActualParameter(this, arg);
 	}
 
-	public Expression E;
+	public final Expression E;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/EmptyActualParameterSequence.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class EmptyActualParameterSequence extends ActualParameterSequence {
@@ -22,8 +23,7 @@ public class EmptyActualParameterSequence extends ActualParameterSequence {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitEmptyActualParameterSequence(this, o);
+	public <TArg, TResult> TResult visit(ActualParameterSequenceVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitEmptyActualParameterSequence(this, arg);
 	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/FuncActualParameter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class FuncActualParameter extends ActualParameter {
@@ -23,10 +25,9 @@ public class FuncActualParameter extends ActualParameter {
 		I = iAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitFuncActualParameter(this, o);
+	public <TArg, TResult> TResult visit(ActualParameterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitFuncActualParameter(this, arg);
 	}
 
-	public Identifier I;
+	public final Identifier I;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/MultipleActualParameterSequence.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class MultipleActualParameterSequence extends ActualParameterSequence {
@@ -25,11 +26,10 @@ public class MultipleActualParameterSequence extends ActualParameterSequence {
 		APS = apsAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitMultipleActualParameterSequence(this, o);
+	public <TArg, TResult> TResult visit(ActualParameterSequenceVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitMultipleActualParameterSequence(this, arg);
 	}
 
-	public ActualParameter AP;
-	public ActualParameterSequence APS;
+	public final ActualParameter AP;
+	public final ActualParameterSequence APS;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/ProcActualParameter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ProcActualParameter extends ActualParameter {
@@ -23,10 +25,9 @@ public class ProcActualParameter extends ActualParameter {
 		I = iAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitProcActualParameter(this, o);
+	public <TArg, TResult> TResult visit(ActualParameterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitProcActualParameter(this, arg);
 	}
 
-	public Identifier I;
+	public final Identifier I;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/SingleActualParameterSequence.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SingleActualParameterSequence extends ActualParameterSequence {
@@ -23,10 +24,9 @@ public class SingleActualParameterSequence extends ActualParameterSequence {
 		AP = apAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSingleActualParameterSequence(this, o);
+	public <TArg, TResult> TResult visit(ActualParameterSequenceVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSingleActualParameterSequence(this, arg);
 	}
 
-	public ActualParameter AP;
+	public final ActualParameter AP;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Actuals/VarActualParameter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Actuals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.ActualParameterVisitor;
+import Triangle.AbstractSyntaxTrees.Vnames.Vname;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class VarActualParameter extends ActualParameter {
@@ -23,10 +25,9 @@ public class VarActualParameter extends ActualParameter {
 		V = vAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitVarActualParameter(this, o);
+	public <TArg, TResult> TResult visit(ActualParameterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitVarActualParameter(this, arg);
 	}
 
-	public Vname V;
+	public final Vname V;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Aggregates/ArrayAggregate.java

@@ -12,11 +12,13 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Aggregates;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Visitors.ArrayAggregateVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class ArrayAggregate extends AST {
+public abstract class ArrayAggregate extends AbstractSyntaxTree {
 
 	public ArrayAggregate(SourcePosition position) {
 		super(position);
@@ -24,4 +26,10 @@ public abstract class ArrayAggregate extends AST {
 	}
 
 	public int elemCount;
+
+	public abstract <TArg, TResult> TResult visit(ArrayAggregateVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(ArrayAggregateVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Aggregates/MultipleArrayAggregate.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Aggregates;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Visitors.ArrayAggregateVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class MultipleArrayAggregate extends ArrayAggregate {
@@ -24,11 +26,10 @@ public class MultipleArrayAggregate extends ArrayAggregate {
 		AA = aaAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitMultipleArrayAggregate(this, o);
+	public <TArg, TResult> TResult visit(ArrayAggregateVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitMultipleArrayAggregate(this, arg);
 	}
 
-	public Expression E;
-	public ArrayAggregate AA;
+	public final Expression E;
+	public final ArrayAggregate AA;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Aggregates/MultipleRecordAggregate.java

@@ -12,26 +12,27 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Aggregates;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.RecordAggregateVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class MultipleRecordAggregate extends RecordAggregate {
 
-	public MultipleRecordAggregate(Identifier iAST, Expression eAST, RecordAggregate raAST,
-			SourcePosition position) {
+	public MultipleRecordAggregate(Identifier iAST, Expression eAST, RecordAggregate raAST, SourcePosition position) {
 		super(position);
 		I = iAST;
 		E = eAST;
 		RA = raAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitMultipleRecordAggregate(this, o);
+	public <TArg, TResult> TResult visit(RecordAggregateVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitMultipleRecordAggregate(this, arg);
 	}
 
-	public Identifier I;
-	public Expression E;
-	public RecordAggregate RA;
+	public final Identifier I;
+	public final Expression E;
+	public final RecordAggregate RA;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Aggregates/RecordAggregate.java

@@ -12,11 +12,14 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Aggregates;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Types.FieldTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.RecordAggregateVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class RecordAggregate extends AST {
+public abstract class RecordAggregate extends AbstractSyntaxTree {
 
 	public RecordAggregate(SourcePosition position) {
 		super(position);
@@ -24,4 +27,10 @@ public abstract class RecordAggregate extends AST {
 	}
 
 	public FieldTypeDenoter type;
+
+	public abstract <TArg, TResult> TResult visit(RecordAggregateVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(RecordAggregateVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Aggregates/SingleArrayAggregate.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Aggregates;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Visitors.ArrayAggregateVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SingleArrayAggregate extends ArrayAggregate {
@@ -23,10 +25,9 @@ public class SingleArrayAggregate extends ArrayAggregate {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSingleArrayAggregate(this, o);
+	public <TArg, TResult> TResult visit(ArrayAggregateVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSingleArrayAggregate(this, arg);
 	}
 
-	public Expression E;
+	public final Expression E;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Aggregates/SingleRecordAggregate.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Aggregates;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.RecordAggregateVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SingleRecordAggregate extends RecordAggregate {
@@ -24,11 +27,10 @@ public class SingleRecordAggregate extends RecordAggregate {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSingleRecordAggregate(this, o);
+	public <TArg, TResult> TResult visit(RecordAggregateVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSingleRecordAggregate(this, arg);
 	}
 
-	public Identifier I;
-	public Expression E;
+	public final Identifier I;
+	public final Expression E;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/AssignCommand.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
+import Triangle.AbstractSyntaxTrees.Vnames.Vname;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class AssignCommand extends Command {
@@ -24,11 +27,10 @@ public class AssignCommand extends Command {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitAssignCommand(this, o);
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitAssignCommand(this, arg);
 	}
 
-	public Vname V;
-	public Expression E;
+	public final Vname V;
+	public final Expression E;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/CallCommand.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.Actuals.ActualParameterSequence;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class CallCommand extends Command {
@@ -24,11 +27,10 @@ public class CallCommand extends Command {
 		APS = apsAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitCallCommand(this, o);
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitCallCommand(this, arg);
 	}
 
-	public Identifier I;
-	public ActualParameterSequence APS;
+	public final Identifier I;
+	public final ActualParameterSequence APS;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/Command.java

@@ -12,13 +12,21 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class Command extends AST {
+public abstract class Command extends AbstractSyntaxTree {
 
 	public Command(SourcePosition position) {
 		super(position);
 	}
+
+	public abstract <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/EmptyCommand.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class EmptyCommand extends Command {
@@ -22,8 +23,7 @@ public class EmptyCommand extends Command {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitEmptyCommand(this, o);
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitEmptyCommand(this, arg);
 	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/IfCommand.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class IfCommand extends Command {
@@ -25,11 +27,10 @@ public class IfCommand extends Command {
 		C2 = c2AST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitIfCommand(this, o);
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitIfCommand(this, arg);
 	}
 
-	public Expression E;
-	public Command C1, C2;
+	public final Expression E;
+	public final Command C1, C2;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/LetCommand.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.Declarations.Declaration;
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class LetCommand extends Command {
@@ -24,11 +26,10 @@ public class LetCommand extends Command {
 		C = cAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitLetCommand(this, o);
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitLetCommand(this, arg);
 	}
 
-	public Declaration D;
-	public Command C;
+	public final Declaration D;
+	public final Command C;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/SequentialCommand.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SequentialCommand extends Command {
@@ -24,10 +25,9 @@ public class SequentialCommand extends Command {
 		C2 = c2AST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSequentialCommand(this, o);
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSequentialCommand(this, arg);
 	}
 
-	public Command C1, C2;
+	public final Command C1, C2;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Commands/WhileCommand.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Commands;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Visitors.CommandVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class WhileCommand extends Command {
@@ -24,11 +26,10 @@ public class WhileCommand extends Command {
 		C = cAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitWhileCommand(this, o);
+	public <TArg, TResult> TResult visit(CommandVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitWhileCommand(this, arg);
 	}
 
-	public Expression E;
-	public Command C;
+	public final Expression E;
+	public final Command C;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/BinaryOperatorDeclaration.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Operator;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class BinaryOperatorDeclaration extends Declaration {
@@ -27,11 +30,10 @@ public class BinaryOperatorDeclaration extends Declaration {
 		RES = resultAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitBinaryOperatorDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitBinaryOperatorDeclaration(this, arg);
 	}
 
-	public Operator O;
-	public TypeDenoter ARG1, ARG2, RES;
+	public final Operator O;
+	public final TypeDenoter ARG1, ARG2, RES;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/ConstDeclaration.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ConstDeclaration extends Declaration {
@@ -24,11 +27,10 @@ public class ConstDeclaration extends Declaration {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitConstDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitConstDeclaration(this, arg);
 	}
 
-	public Identifier I;
-	public Expression E;
+	public final Identifier I;
+	public final Expression E;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/Declaration.java

@@ -12,11 +12,13 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class Declaration extends AST {
+public abstract class Declaration extends AbstractSyntaxTree {
 
 	public Declaration(SourcePosition position) {
 		super(position);
@@ -24,4 +26,10 @@ public abstract class Declaration extends AST {
 	}
 
 	public boolean duplicated;
+
+	public abstract <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/FuncDeclaration.java

@@ -12,8 +12,13 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Formals.FormalParameterSequence;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class FuncDeclaration extends Declaration {
@@ -27,13 +32,12 @@ public class FuncDeclaration extends Declaration {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitFuncDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitFuncDeclaration(this, arg);
 	}
 
-	public Identifier I;
-	public FormalParameterSequence FPS;
+	public final Identifier I;
+	public final FormalParameterSequence FPS;
 	public TypeDenoter T;
-	public Expression E;
+	public final Expression E;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/ProcDeclaration.java

@@ -12,8 +12,12 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.Commands.Command;
+import Triangle.AbstractSyntaxTrees.Formals.FormalParameterSequence;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ProcDeclaration extends Declaration {
@@ -25,12 +29,11 @@ public class ProcDeclaration extends Declaration {
 		C = cAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitProcDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitProcDeclaration(this, arg);
 	}
 
-	public Identifier I;
-	public FormalParameterSequence FPS;
-	public Command C;
+	public final Identifier I;
+	public final FormalParameterSequence FPS;
+	public final Command C;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/SequentialDeclaration.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SequentialDeclaration extends Declaration {
@@ -24,10 +25,9 @@ public class SequentialDeclaration extends Declaration {
 		D2 = d2AST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSequentialDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSequentialDeclaration(this, arg);
 	}
 
-	public Declaration D1, D2;
+	public final Declaration D1, D2;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/UnaryOperatorDeclaration.java

@@ -12,25 +12,26 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Operator;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class UnaryOperatorDeclaration extends Declaration {
 
-	public UnaryOperatorDeclaration(Operator oAST, TypeDenoter argAST, TypeDenoter resultAST,
-			SourcePosition position) {
+	public UnaryOperatorDeclaration(Operator oAST, TypeDenoter argAST, TypeDenoter resultAST, SourcePosition position) {
 		super(position);
 		O = oAST;
 		ARG = argAST;
 		RES = resultAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitUnaryOperatorDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitUnaryOperatorDeclaration(this, arg);
 	}
 
-	public Operator O;
-	public TypeDenoter ARG, RES;
+	public final Operator O;
+	public final TypeDenoter ARG, RES;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Declarations/VarDeclaration.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Declarations;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class VarDeclaration extends Declaration {
@@ -24,11 +27,10 @@ public class VarDeclaration extends Declaration {
 		T = tAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitVarDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitVarDeclaration(this, arg);
 	}
 
-	public Identifier I;
+	public final Identifier I;
 	public TypeDenoter T;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/ArrayExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Aggregates.ArrayAggregate;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ArrayExpression extends Expression {
@@ -23,10 +25,9 @@ public class ArrayExpression extends Expression {
 		AA = aaAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitArrayExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitArrayExpression(this, arg);
 	}
 
-	public ArrayAggregate AA;
+	public final ArrayAggregate AA;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/BinaryExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Operator;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class BinaryExpression extends Expression {
@@ -25,11 +27,10 @@ public class BinaryExpression extends Expression {
 		E2 = e2AST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitBinaryExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitBinaryExpression(this, arg);
 	}
 
-	public Expression E1, E2;
-	public Operator O;
+	public final Expression E1, E2;
+	public final Operator O;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/CallExpression.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Actuals.ActualParameterSequence;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class CallExpression extends Expression {
@@ -24,11 +27,10 @@ public class CallExpression extends Expression {
 		APS = apsAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitCallExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitCallExpression(this, arg);
 	}
 
-	public Identifier I;
-	public ActualParameterSequence APS;
+	public final Identifier I;
+	public final ActualParameterSequence APS;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/CharacterExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Terminals.CharacterLiteral;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class CharacterExpression extends Expression {
@@ -23,10 +25,9 @@ public class CharacterExpression extends Expression {
 		CL = clAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitCharacterExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitCharacterExpression(this, arg);
 	}
 
-	public CharacterLiteral CL;
+	public final CharacterLiteral CL;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/EmptyExpression.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class EmptyExpression extends Expression {
@@ -22,8 +23,7 @@ public class EmptyExpression extends Expression {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitEmptyExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitEmptyExpression(this, arg);
 	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/Expression.java

@@ -12,11 +12,14 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class Expression extends AST {
+public abstract class Expression extends AbstractSyntaxTree {
 
 	public Expression(SourcePosition position) {
 		super(position);
@@ -24,4 +27,10 @@ public abstract class Expression extends AST {
 	}
 
 	public TypeDenoter type;
+
+	public abstract <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/IfExpression.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class IfExpression extends Expression {
@@ -25,10 +26,9 @@ public class IfExpression extends Expression {
 		E3 = e3AST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitIfExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitIfExpression(this, arg);
 	}
 
-	public Expression E1, E2, E3;
+	public final Expression E1, E2, E3;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/IntegerExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Terminals.IntegerLiteral;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class IntegerExpression extends Expression {
@@ -23,10 +25,9 @@ public class IntegerExpression extends Expression {
 		IL = ilAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitIntegerExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitIntegerExpression(this, arg);
 	}
 
-	public IntegerLiteral IL;
+	public final IntegerLiteral IL;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/LetExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Declarations.Declaration;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class LetExpression extends Expression {
@@ -24,11 +26,10 @@ public class LetExpression extends Expression {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitLetExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitLetExpression(this, arg);
 	}
 
-	public Declaration D;
-	public Expression E;
+	public final Declaration D;
+	public final Expression E;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/RecordExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Aggregates.RecordAggregate;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class RecordExpression extends Expression {
@@ -23,10 +25,9 @@ public class RecordExpression extends Expression {
 		RA = raAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitRecordExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitRecordExpression(this, arg);
 	}
 
-	public RecordAggregate RA;
+	public final RecordAggregate RA;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/UnaryExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Operator;
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class UnaryExpression extends Expression {
@@ -24,11 +26,10 @@ public class UnaryExpression extends Expression {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitUnaryExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitUnaryExpression(this, arg);
 	}
 
-	public Expression E;
-	public Operator O;
+	public final Expression E;
+	public final Operator O;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Expressions/VnameExpression.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Expressions;
 
+import Triangle.AbstractSyntaxTrees.Visitors.ExpressionVisitor;
+import Triangle.AbstractSyntaxTrees.Vnames.Vname;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class VnameExpression extends Expression {
@@ -23,10 +25,9 @@ public class VnameExpression extends Expression {
 		V = vAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitVnameExpression(this, o);
+	public <TArg, TResult> TResult visit(ExpressionVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitVnameExpression(this, arg);
 	}
 
-	public Vname V;
+	public final Vname V;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/ConstFormalParameter.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ConstFormalParameter extends FormalParameter {
@@ -24,20 +27,20 @@ public class ConstFormalParameter extends FormalParameter {
 		T = tAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitConstFormalParameter(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitConstFormalParameter(this, arg);
 	}
 
-	public Identifier I;
-	public TypeDenoter T;
-
 	@Override
 	public boolean equals(Object fpAST) {
 		if (fpAST instanceof ConstFormalParameter) {
-			ConstFormalParameter cfpAST = (ConstFormalParameter) fpAST;
+			var cfpAST = (ConstFormalParameter) fpAST;
 			return T.equals(cfpAST.T);
-		} else
+		} else {
 			return false;
 		}
+	}
+
+	public final Identifier I;
+	public TypeDenoter T;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/EmptyFormalParameterSequence.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.FormalParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class EmptyFormalParameterSequence extends FormalParameterSequence {
@@ -22,9 +23,8 @@ public class EmptyFormalParameterSequence extends FormalParameterSequence {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitEmptyFormalParameterSequence(this, o);
+	public <TArg, TResult> TResult visit(FormalParameterSequenceVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitEmptyFormalParameterSequence(this, arg);
 	}
 
 	@Override

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/FormalParameter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Declarations.Declaration;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public abstract class FormalParameter extends Declaration {
@@ -25,4 +27,9 @@ public abstract class FormalParameter extends Declaration {
 	@Override
 	public abstract boolean equals(Object fpAST);
 
+	public abstract <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/FormalParameterSequence.java

@@ -12,11 +12,13 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Visitors.FormalParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class FormalParameterSequence extends AST {
+public abstract class FormalParameterSequence extends AbstractSyntaxTree {
 
 	public FormalParameterSequence(SourcePosition position) {
 		super(position);
@@ -24,4 +26,10 @@ public abstract class FormalParameterSequence extends AST {
 
 	@Override
 	public abstract boolean equals(Object fpsAST);
+
+	public abstract <TArg, TResult> TResult visit(FormalParameterSequenceVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(FormalParameterSequenceVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/FuncFormalParameter.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class FuncFormalParameter extends FormalParameter {
@@ -26,9 +29,8 @@ public class FuncFormalParameter extends FormalParameter {
 		T = tAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitFuncFormalParameter(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitFuncFormalParameter(this, arg);
 	}
 
 	@Override
@@ -40,7 +42,7 @@ public class FuncFormalParameter extends FormalParameter {
 			return false;
 	}
 
-	public Identifier I;
-	public FormalParameterSequence FPS;
+	public final Identifier I;
+	public final FormalParameterSequence FPS;
 	public TypeDenoter T;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/MultipleFormalParameterSequence.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.FormalParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class MultipleFormalParameterSequence extends FormalParameterSequence {
@@ -25,9 +26,8 @@ public class MultipleFormalParameterSequence extends FormalParameterSequence {
 		FPS = fpsAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitMultipleFormalParameterSequence(this, o);
+	public <TArg, TResult> TResult visit(FormalParameterSequenceVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitMultipleFormalParameterSequence(this, arg);
 	}
 
 	@Override
@@ -35,10 +35,11 @@ public class MultipleFormalParameterSequence extends FormalParameterSequence {
 		if (fpsAST instanceof MultipleFormalParameterSequence) {
 			MultipleFormalParameterSequence mfpsAST = (MultipleFormalParameterSequence) fpsAST;
 			return FP.equals(mfpsAST.FP) && FPS.equals(mfpsAST.FPS);
-		} else
+		} else {
 			return false;
 		}
+	}
 
-	public FormalParameter FP;
-	public FormalParameterSequence FPS;
+	public final FormalParameter FP;
+	public final FormalParameterSequence FPS;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/ProcFormalParameter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ProcFormalParameter extends FormalParameter {
@@ -24,20 +26,20 @@ public class ProcFormalParameter extends FormalParameter {
 		FPS = fpsAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitProcFormalParameter(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitProcFormalParameter(this, arg);
 	}
 
-	public Identifier I;
-	public FormalParameterSequence FPS;
-
 	@Override
 	public boolean equals(Object fpAST) {
 		if (fpAST instanceof ProcFormalParameter) {
 			ProcFormalParameter pfpAST = (ProcFormalParameter) fpAST;
 			return FPS.equals(pfpAST.FPS);
-		} else
+		} else {
 			return false;
 		}
+	}
+
+	public final Identifier I;
+	public final FormalParameterSequence FPS;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/SingleFormalParameterSequence.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.FormalParameterSequenceVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SingleFormalParameterSequence extends FormalParameterSequence {
@@ -23,9 +24,8 @@ public class SingleFormalParameterSequence extends FormalParameterSequence {
 		FP = fpAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSingleFormalParameterSequence(this, o);
+	public <TArg, TResult> TResult visit(FormalParameterSequenceVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSingleFormalParameterSequence(this, arg);
 	}
 
 	@Override
@@ -33,9 +33,10 @@ public class SingleFormalParameterSequence extends FormalParameterSequence {
 		if (fpsAST instanceof SingleFormalParameterSequence) {
 			SingleFormalParameterSequence sfpsAST = (SingleFormalParameterSequence) fpsAST;
 			return FP.equals(sfpsAST.FP);
-		} else
+		} else {
 			return false;
 		}
+	}
 
-	public FormalParameter FP;
+	public final FormalParameter FP;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Formals/VarFormalParameter.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Formals;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class VarFormalParameter extends FormalParameter {
@@ -24,20 +27,20 @@ public class VarFormalParameter extends FormalParameter {
 		T = tAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitVarFormalParameter(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitVarFormalParameter(this, arg);
 	}
 
-	public Identifier I;
-	public TypeDenoter T;
-
 	@Override
 	public boolean equals(Object fpAST) {
 		if (fpAST instanceof VarFormalParameter) {
 			VarFormalParameter vfpAST = (VarFormalParameter) fpAST;
 			return T.equals(vfpAST.T);
-		} else
+		} else {
 			return false;
 		}
+	}
+
+	public final Identifier I;
+	public TypeDenoter T;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Program.java

@@ -14,19 +14,24 @@
 
 package Triangle.AbstractSyntaxTrees;
 
+import Triangle.AbstractSyntaxTrees.Commands.Command;
+import Triangle.AbstractSyntaxTrees.Visitors.ProgramVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public class Program extends AST {
+public class Program extends AbstractSyntaxTree {
 
 	public Program(Command cAST, SourcePosition position) {
 		super(position);
 		C = cAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitProgram(this, o);
+	public Command C;
+
+	public <TArg, TResult> TResult visit(ProgramVisitor<TArg, TResult> visitor, TArg arg) {
+		return visitor.visitProgram(this, arg);
 	}
 
-	public Command C;
+	public <TResult> TResult visit(ProgramVisitor<Void, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Terminals/CharacterLiteral.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Terminals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.LiteralVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class CharacterLiteral extends Terminal {
@@ -22,9 +23,15 @@ public class CharacterLiteral extends Terminal {
 		super(spelling, position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitCharacterLiteral(this, o);
+	public <TArg, TResult> TResult visit(LiteralVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitCharacterLiteral(this, arg);
 	}
 
+	public <TArg, TResult> TResult visit(LiteralVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
+
+	public int getValue() {
+		return spelling.charAt(1);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Terminals/Identifier.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Terminals;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.IdentifierVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class Identifier extends Terminal {
@@ -24,11 +27,14 @@ public class Identifier extends Terminal {
 		decl = null;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitIdentifier(this, o);
+	public TypeDenoter type;
+	public AbstractSyntaxTree decl; // Either a Declaration or a FieldTypeDenoter
+
+	public <TArg, TResult> TResult visit(IdentifierVisitor<TArg, TResult> visitor, TArg arg) {
+		return visitor.visitIdentifier(this, arg);
 	}
 
-	public TypeDenoter type;
-	public AST decl; // Either a Declaration or a FieldTypeDenoter
+	public <TArg, TResult> TResult visit(IdentifierVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Terminals/IntegerLiteral.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Terminals;
 
+import Triangle.AbstractSyntaxTrees.Visitors.LiteralVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class IntegerLiteral extends Terminal {
@@ -22,9 +23,15 @@ public class IntegerLiteral extends Terminal {
 		super(spelling, position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitIntegerLiteral(this, o);
+	public <TArg, TResult> TResult visit(LiteralVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitIntegerLiteral(this, arg);
 	}
 
+	public <TArg, TResult> TResult visit(LiteralVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
+
+	public int getValue() {
+		return Integer.parseInt(spelling);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Terminals/Operator.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Terminals;
 
+import Triangle.AbstractSyntaxTrees.Declarations.Declaration;
+import Triangle.AbstractSyntaxTrees.Visitors.OperatorVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class Operator extends Terminal {
@@ -23,10 +25,13 @@ public class Operator extends Terminal {
 		decl = null;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitOperator(this, o);
+	public Declaration decl;
+
+	public <TArg, TResult> TResult visit(OperatorVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitOperator(this, arg);
 	}
 
-	public Declaration decl;
+	public <TArg, TResult> TResult visit(OperatorVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Terminals/Terminal.java

@@ -12,11 +12,12 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Terminals;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-abstract public class Terminal extends AST {
+public abstract class Terminal extends AbstractSyntaxTree {
 
 	public Terminal(String spelling, SourcePosition position) {
 		super(position);

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/AnyTypeDenoter.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class AnyTypeDenoter extends TypeDenoter {
@@ -22,9 +23,8 @@ public class AnyTypeDenoter extends TypeDenoter {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitAnyTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitAnyTypeDenoter(this, arg);
 	}
 
 	@Override

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/ArrayTypeDenoter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Terminals.IntegerLiteral;
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ArrayTypeDenoter extends TypeDenoter {
@@ -24,22 +26,22 @@ public class ArrayTypeDenoter extends TypeDenoter {
 		T = tAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitArrayTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitArrayTypeDenoter(this, arg);
 	}
 
 	@Override
 	public boolean equals(Object obj) {
-		if (obj != null && obj instanceof ErrorTypeDenoter)
+		if (obj != null && obj instanceof ErrorTypeDenoter) {
 			return true;
-		else if (obj != null && obj instanceof ArrayTypeDenoter)
+		} else if (obj != null && obj instanceof ArrayTypeDenoter) {
 			return this.IL.spelling.compareTo(((ArrayTypeDenoter) obj).IL.spelling) == 0
 					&& this.T.equals(((ArrayTypeDenoter) obj).T);
-		else
+		} else {
 			return false;
 		}
+	}
 
-	public IntegerLiteral IL;
+	public final IntegerLiteral IL;
 	public TypeDenoter T;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/BoolTypeDenoter.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class BoolTypeDenoter extends TypeDenoter {
@@ -22,16 +23,16 @@ public class BoolTypeDenoter extends TypeDenoter {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitBoolTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitBoolTypeDenoter(this, arg);
 	}
 
 	@Override
 	public boolean equals(Object obj) {
-		if ((obj != null) && (obj instanceof ErrorTypeDenoter))
+		if ((obj != null) && (obj instanceof ErrorTypeDenoter)) {
 			return true;
-		else
+		} else {
 			return ((obj != null) && (obj instanceof BoolTypeDenoter));
 		}
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/CharTypeDenoter.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class CharTypeDenoter extends TypeDenoter {
@@ -22,16 +23,16 @@ public class CharTypeDenoter extends TypeDenoter {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitCharTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitCharTypeDenoter(this, arg);
 	}
 
 	@Override
 	public boolean equals(Object obj) {
-		if (obj != null && obj instanceof ErrorTypeDenoter)
+		if (obj != null && obj instanceof ErrorTypeDenoter) {
 			return true;
-		else
+		} else {
 			return (obj != null && obj instanceof CharTypeDenoter);
 		}
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/ErrorTypeDenoter.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class ErrorTypeDenoter extends TypeDenoter {
@@ -22,9 +23,8 @@ public class ErrorTypeDenoter extends TypeDenoter {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitErrorTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitErrorTypeDenoter(this, arg);
 	}
 
 	@Override

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/FieldTypeDenoter.java

@@ -12,7 +12,7 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
@@ -21,7 +21,4 @@ public abstract class FieldTypeDenoter extends TypeDenoter {
 	public FieldTypeDenoter(SourcePosition position) {
 		super(position);
 	}
-
-	@Override
-	public abstract boolean equals(Object obj);
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/IntTypeDenoter.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class IntTypeDenoter extends TypeDenoter {
@@ -22,16 +23,16 @@ public class IntTypeDenoter extends TypeDenoter {
 		super(position);
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitIntTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitIntTypeDenoter(this, arg);
 	}
 
 	@Override
 	public boolean equals(Object obj) {
-		if (obj != null && obj instanceof ErrorTypeDenoter)
+		if (obj != null && obj instanceof ErrorTypeDenoter) {
 			return true;
-		else
+		} else {
 			return (obj != null && obj instanceof IntTypeDenoter);
 		}
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/MultipleFieldTypeDenoter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class MultipleFieldTypeDenoter extends FieldTypeDenoter {
@@ -26,9 +28,8 @@ public class MultipleFieldTypeDenoter extends FieldTypeDenoter {
 		FT = ftAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitMultipleFieldTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitMultipleFieldTypeDenoter(this, arg);
 	}
 
 	@Override
@@ -36,11 +37,12 @@ public class MultipleFieldTypeDenoter extends FieldTypeDenoter {
 		if (obj != null && obj instanceof MultipleFieldTypeDenoter) {
 			MultipleFieldTypeDenoter ft = (MultipleFieldTypeDenoter) obj;
 			return (this.I.spelling.compareTo(ft.I.spelling) == 0) && this.T.equals(ft.T) && this.FT.equals(ft.FT);
-		} else
+		} else {
 			return false;
 		}
+	}
 
-	public Identifier I;
+	public final Identifier I;
 	public TypeDenoter T;
 	public FieldTypeDenoter FT;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/RecordTypeDenoter.java

@@ -12,8 +12,9 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class RecordTypeDenoter extends TypeDenoter {
@@ -23,20 +24,20 @@ public class RecordTypeDenoter extends TypeDenoter {
 		FT = ftAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitRecordTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitRecordTypeDenoter(this, arg);
 	}
 
 	@Override
 	public boolean equals(Object obj) {
-		if (obj != null && obj instanceof ErrorTypeDenoter)
+		if (obj != null && obj instanceof ErrorTypeDenoter) {
 			return true;
-		else if (obj != null && obj instanceof RecordTypeDenoter)
+		} else if (obj != null && obj instanceof RecordTypeDenoter) {
 			return this.FT.equals(((RecordTypeDenoter) obj).FT);
-		else
+		} else {
 			return false;
 		}
+	}
 
 	public FieldTypeDenoter FT;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/SimpleTypeDenoter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SimpleTypeDenoter extends TypeDenoter {
@@ -23,9 +25,8 @@ public class SimpleTypeDenoter extends TypeDenoter {
 		I = iAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSimpleTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSimpleTypeDenoter(this, arg);
 	}
 
 	@Override
@@ -33,5 +34,5 @@ public class SimpleTypeDenoter extends TypeDenoter {
 		return false; // should not happen
 	}
 
-	public Identifier I;
+	public final Identifier I;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/SingleFieldTypeDenoter.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SingleFieldTypeDenoter extends FieldTypeDenoter {
@@ -24,9 +26,8 @@ public class SingleFieldTypeDenoter extends FieldTypeDenoter {
 		T = tAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSingleFieldTypeDenoter(this, o);
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSingleFieldTypeDenoter(this, arg);
 	}
 
 	@Override
@@ -34,10 +35,11 @@ public class SingleFieldTypeDenoter extends FieldTypeDenoter {
 		if (obj != null && obj instanceof SingleFieldTypeDenoter) {
 			SingleFieldTypeDenoter ft = (SingleFieldTypeDenoter) obj;
 			return (this.I.spelling.compareTo(ft.I.spelling) == 0) && this.T.equals(ft.T);
-		} else
+		} else {
 			return false;
 		}
+	}
 
-	public Identifier I;
+	public final Identifier I;
 	public TypeDenoter T;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/TypeDeclaration.java

@@ -12,8 +12,11 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.Declarations.Declaration;
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.DeclarationVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class TypeDeclaration extends Declaration {
@@ -24,11 +27,10 @@ public class TypeDeclaration extends Declaration {
 		T = tAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitTypeDeclaration(this, o);
+	public <TArg, TResult> TResult visit(DeclarationVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitTypeDeclaration(this, arg);
 	}
 
-	public Identifier I;
+	public final Identifier I;
 	public TypeDenoter T;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Types/TypeDenoter.java

@@ -12,11 +12,13 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Types;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Visitors.TypeDenoterVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class TypeDenoter extends AST {
+public abstract class TypeDenoter extends AbstractSyntaxTree {
 
 	public TypeDenoter(SourcePosition position) {
 		super(position);
@@ -25,4 +27,9 @@ public abstract class TypeDenoter extends AST {
 	@Override
 	public abstract boolean equals(Object obj);
 
+	public abstract <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(TypeDenoterVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitor.java

@@ -1,154 +0,0 @@
-/*
- * @(#)Visitor.java                        2.1 2003/10/07
- *
- * Copyright (C) 1999, 2003 D.A. Watt and D.F. Brown
- * Dept. of Computing Science, University of Glasgow, Glasgow G12 8QQ Scotland
- * and School of Computer and Math Sciences, The Robert Gordon University,
- * St. Andrew Street, Aberdeen AB25 1HG, Scotland.
- * All rights reserved.
- *
- * This software is provided free for educational use only. It may
- * not be used for commercial purposes without the prior written permission
- * of the authors.
- */
-
-package Triangle.AbstractSyntaxTrees;
-
-public interface Visitor {
-
-	// Commands
-	Object visitAssignCommand(AssignCommand ast, Object o);
-
-	Object visitCallCommand(CallCommand ast, Object o);
-
-	Object visitEmptyCommand(EmptyCommand ast, Object o);
-
-	Object visitIfCommand(IfCommand ast, Object o);
-
-	Object visitLetCommand(LetCommand ast, Object o);
-
-	Object visitSequentialCommand(SequentialCommand ast, Object o);
-
-	Object visitWhileCommand(WhileCommand ast, Object o);
-
-	// Expressions
-	Object visitArrayExpression(ArrayExpression ast, Object o);
-
-	Object visitBinaryExpression(BinaryExpression ast, Object o);
-
-	Object visitCallExpression(CallExpression ast, Object o);
-
-	Object visitCharacterExpression(CharacterExpression ast, Object o);
-
-	Object visitEmptyExpression(EmptyExpression ast, Object o);
-
-	Object visitIfExpression(IfExpression ast, Object o);
-
-	Object visitIntegerExpression(IntegerExpression ast, Object o);
-
-	Object visitLetExpression(LetExpression ast, Object o);
-
-	Object visitRecordExpression(RecordExpression ast, Object o);
-
-	Object visitUnaryExpression(UnaryExpression ast, Object o);
-
-	Object visitVnameExpression(VnameExpression ast, Object o);
-
-	// Declarations
-	Object visitBinaryOperatorDeclaration(BinaryOperatorDeclaration ast, Object o);
-
-	Object visitConstDeclaration(ConstDeclaration ast, Object o);
-
-	Object visitFuncDeclaration(FuncDeclaration ast, Object o);
-
-	Object visitProcDeclaration(ProcDeclaration ast, Object o);
-
-	Object visitSequentialDeclaration(SequentialDeclaration ast, Object o);
-
-	Object visitTypeDeclaration(TypeDeclaration ast, Object o);
-
-	Object visitUnaryOperatorDeclaration(UnaryOperatorDeclaration ast, Object o);
-
-	Object visitVarDeclaration(VarDeclaration ast, Object o);
-
-	// Array Aggregates
-	Object visitMultipleArrayAggregate(MultipleArrayAggregate ast, Object o);
-
-	Object visitSingleArrayAggregate(SingleArrayAggregate ast, Object o);
-
-	// Record Aggregates
-	Object visitMultipleRecordAggregate(MultipleRecordAggregate ast, Object o);
-
-	Object visitSingleRecordAggregate(SingleRecordAggregate ast, Object o);
-
-	// Formal Parameters
-	Object visitConstFormalParameter(ConstFormalParameter ast, Object o);
-
-	Object visitFuncFormalParameter(FuncFormalParameter ast, Object o);
-
-	Object visitProcFormalParameter(ProcFormalParameter ast, Object o);
-
-	Object visitVarFormalParameter(VarFormalParameter ast, Object o);
-
-	Object visitEmptyFormalParameterSequence(EmptyFormalParameterSequence ast, Object o);
-
-	Object visitMultipleFormalParameterSequence(MultipleFormalParameterSequence ast, Object o);
-
-	Object visitSingleFormalParameterSequence(SingleFormalParameterSequence ast, Object o);
-
-	// Actual Parameters
-	Object visitConstActualParameter(ConstActualParameter ast, Object o);
-
-	Object visitFuncActualParameter(FuncActualParameter ast, Object o);
-
-	Object visitProcActualParameter(ProcActualParameter ast, Object o);
-
-	Object visitVarActualParameter(VarActualParameter ast, Object o);
-
-	Object visitEmptyActualParameterSequence(EmptyActualParameterSequence ast, Object o);
-
-	Object visitMultipleActualParameterSequence(MultipleActualParameterSequence ast, Object o);
-
-	Object visitSingleActualParameterSequence(SingleActualParameterSequence ast, Object o);
-
-	// Type Denoters
-	Object visitAnyTypeDenoter(AnyTypeDenoter ast, Object o);
-
-	Object visitArrayTypeDenoter(ArrayTypeDenoter ast, Object o);
-
-	Object visitBoolTypeDenoter(BoolTypeDenoter ast, Object o);
-
-	Object visitCharTypeDenoter(CharTypeDenoter ast, Object o);
-
-	Object visitErrorTypeDenoter(ErrorTypeDenoter ast, Object o);
-
-	Object visitSimpleTypeDenoter(SimpleTypeDenoter ast, Object o);
-
-	Object visitIntTypeDenoter(IntTypeDenoter ast, Object o);
-
-	Object visitRecordTypeDenoter(RecordTypeDenoter ast, Object o);
-
-	Object visitMultipleFieldTypeDenoter(MultipleFieldTypeDenoter ast, Object o);
-
-	Object visitSingleFieldTypeDenoter(SingleFieldTypeDenoter ast, Object o);
-
-	// Literals, Identifiers and Operators
-	Object visitCharacterLiteral(CharacterLiteral ast, Object o);
-
-	Object visitIdentifier(Identifier ast, Object o);
-
-	Object visitIntegerLiteral(IntegerLiteral ast, Object o);
-
-	Object visitOperator(Operator ast, Object o);
-
-	// Value-or-variable names
-	Object visitDotVname(DotVname ast, Object o);
-
-	Object visitSimpleVname(SimpleVname ast, Object o);
-
-	Object visitSubscriptVname(SubscriptVname ast, Object o);
-
-	// Programs
-	Object visitProgram(Program ast, Object o);
-
-}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/ActualParameterSequenceVisitor.java

@@ -0,0 +1,15 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Actuals.EmptyActualParameterSequence;
+import Triangle.AbstractSyntaxTrees.Actuals.MultipleActualParameterSequence;
+import Triangle.AbstractSyntaxTrees.Actuals.SingleActualParameterSequence;
+
+public interface ActualParameterSequenceVisitor<TArg, TResult> {
+
+	TResult visitEmptyActualParameterSequence(EmptyActualParameterSequence ast, TArg arg);
+
+	TResult visitMultipleActualParameterSequence(MultipleActualParameterSequence ast, TArg arg);
+
+	TResult visitSingleActualParameterSequence(SingleActualParameterSequence ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/ActualParameterVisitor.java

@@ -0,0 +1,18 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Actuals.ConstActualParameter;
+import Triangle.AbstractSyntaxTrees.Actuals.FuncActualParameter;
+import Triangle.AbstractSyntaxTrees.Actuals.ProcActualParameter;
+import Triangle.AbstractSyntaxTrees.Actuals.VarActualParameter;
+
+public interface ActualParameterVisitor<TArg, TResult> {
+
+	TResult visitConstActualParameter(ConstActualParameter ast, TArg arg);
+
+	TResult visitFuncActualParameter(FuncActualParameter ast, TArg arg);
+
+	TResult visitProcActualParameter(ProcActualParameter ast, TArg arg);
+
+	TResult visitVarActualParameter(VarActualParameter ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/ArrayAggregateVisitor.java

@@ -0,0 +1,12 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Aggregates.MultipleArrayAggregate;
+import Triangle.AbstractSyntaxTrees.Aggregates.SingleArrayAggregate;
+
+public interface ArrayAggregateVisitor<TArg, TResult> {
+
+	TResult visitMultipleArrayAggregate(MultipleArrayAggregate ast, TArg arg);
+
+	TResult visitSingleArrayAggregate(SingleArrayAggregate ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/CommandVisitor.java

@@ -0,0 +1,27 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Commands.AssignCommand;
+import Triangle.AbstractSyntaxTrees.Commands.CallCommand;
+import Triangle.AbstractSyntaxTrees.Commands.EmptyCommand;
+import Triangle.AbstractSyntaxTrees.Commands.IfCommand;
+import Triangle.AbstractSyntaxTrees.Commands.LetCommand;
+import Triangle.AbstractSyntaxTrees.Commands.SequentialCommand;
+import Triangle.AbstractSyntaxTrees.Commands.WhileCommand;
+
+public interface CommandVisitor<TArg, TResult> {
+
+	TResult visitAssignCommand(AssignCommand ast, TArg arg);
+
+	TResult visitCallCommand(CallCommand ast, TArg arg);
+
+	TResult visitEmptyCommand(EmptyCommand ast, TArg arg);
+
+	TResult visitIfCommand(IfCommand ast, TArg arg);
+
+	TResult visitLetCommand(LetCommand ast, TArg arg);
+
+	TResult visitSequentialCommand(SequentialCommand ast, TArg arg);
+
+	TResult visitWhileCommand(WhileCommand ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/DeclarationVisitor.java

@@ -0,0 +1,30 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Declarations.BinaryOperatorDeclaration;
+import Triangle.AbstractSyntaxTrees.Declarations.ConstDeclaration;
+import Triangle.AbstractSyntaxTrees.Declarations.FuncDeclaration;
+import Triangle.AbstractSyntaxTrees.Declarations.ProcDeclaration;
+import Triangle.AbstractSyntaxTrees.Declarations.SequentialDeclaration;
+import Triangle.AbstractSyntaxTrees.Declarations.UnaryOperatorDeclaration;
+import Triangle.AbstractSyntaxTrees.Declarations.VarDeclaration;
+import Triangle.AbstractSyntaxTrees.Types.TypeDeclaration;
+
+public interface DeclarationVisitor<TArg, TResult> extends FormalParameterVisitor<TArg, TResult> {
+
+	TResult visitBinaryOperatorDeclaration(BinaryOperatorDeclaration ast, TArg arg);
+
+	TResult visitConstDeclaration(ConstDeclaration ast, TArg arg);
+
+	TResult visitFuncDeclaration(FuncDeclaration ast, TArg arg);
+
+	TResult visitProcDeclaration(ProcDeclaration ast, TArg arg);
+
+	TResult visitSequentialDeclaration(SequentialDeclaration ast, TArg arg);
+
+	TResult visitTypeDeclaration(TypeDeclaration ast, TArg arg);
+
+	TResult visitUnaryOperatorDeclaration(UnaryOperatorDeclaration ast, TArg arg);
+
+	TResult visitVarDeclaration(VarDeclaration ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/ExpressionVisitor.java

@@ -0,0 +1,39 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Expressions.ArrayExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.BinaryExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.CallExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.CharacterExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.EmptyExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.IfExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.IntegerExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.LetExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.RecordExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.UnaryExpression;
+import Triangle.AbstractSyntaxTrees.Expressions.VnameExpression;
+
+public interface ExpressionVisitor<TArg, TResult> {
+
+	TResult visitArrayExpression(ArrayExpression ast, TArg arg);
+
+	TResult visitBinaryExpression(BinaryExpression ast, TArg arg);
+
+	TResult visitCallExpression(CallExpression ast, TArg arg);
+
+	TResult visitCharacterExpression(CharacterExpression ast, TArg arg);
+
+	TResult visitEmptyExpression(EmptyExpression ast, TArg arg);
+
+	TResult visitIfExpression(IfExpression ast, TArg arg);
+
+	TResult visitIntegerExpression(IntegerExpression ast, TArg arg);
+
+	TResult visitLetExpression(LetExpression ast, TArg arg);
+
+	TResult visitRecordExpression(RecordExpression ast, TArg arg);
+
+	TResult visitUnaryExpression(UnaryExpression ast, TArg arg);
+
+	TResult visitVnameExpression(VnameExpression ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/FieldTypeDenoterVisitor.java

@@ -0,0 +1,12 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Types.MultipleFieldTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.SingleFieldTypeDenoter;
+
+public interface FieldTypeDenoterVisitor<TArg, TResult> {
+
+	TResult visitMultipleFieldTypeDenoter(MultipleFieldTypeDenoter ast, TArg arg);
+
+	TResult visitSingleFieldTypeDenoter(SingleFieldTypeDenoter ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/FormalParameterSequenceVisitor.java

@@ -0,0 +1,15 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Formals.EmptyFormalParameterSequence;
+import Triangle.AbstractSyntaxTrees.Formals.MultipleFormalParameterSequence;
+import Triangle.AbstractSyntaxTrees.Formals.SingleFormalParameterSequence;
+
+public interface FormalParameterSequenceVisitor<TArg, TResult> {
+
+	TResult visitEmptyFormalParameterSequence(EmptyFormalParameterSequence ast, TArg arg);
+
+	TResult visitMultipleFormalParameterSequence(MultipleFormalParameterSequence ast, TArg arg);
+
+	TResult visitSingleFormalParameterSequence(SingleFormalParameterSequence ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/FormalParameterVisitor.java

@@ -0,0 +1,18 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Formals.ConstFormalParameter;
+import Triangle.AbstractSyntaxTrees.Formals.FuncFormalParameter;
+import Triangle.AbstractSyntaxTrees.Formals.ProcFormalParameter;
+import Triangle.AbstractSyntaxTrees.Formals.VarFormalParameter;
+
+public interface FormalParameterVisitor<TArg, TResult> {
+
+	TResult visitConstFormalParameter(ConstFormalParameter ast, TArg arg);
+
+	TResult visitFuncFormalParameter(FuncFormalParameter ast, TArg arg);
+
+	TResult visitProcFormalParameter(ProcFormalParameter ast, TArg arg);
+
+	TResult visitVarFormalParameter(VarFormalParameter ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/IdentifierVisitor.java

@@ -0,0 +1,9 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+
+public interface IdentifierVisitor<TArg, TResult> {
+
+	TResult visitIdentifier(Identifier ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/LiteralVisitor.java

@@ -0,0 +1,12 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Terminals.CharacterLiteral;
+import Triangle.AbstractSyntaxTrees.Terminals.IntegerLiteral;
+
+public interface LiteralVisitor<TArg, TResult> {
+
+	TResult visitCharacterLiteral(CharacterLiteral ast, TArg arg);
+
+	TResult visitIntegerLiteral(IntegerLiteral ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/OperatorVisitor.java

@@ -0,0 +1,9 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Terminals.Operator;
+
+public interface OperatorVisitor<TArg, TResult> {
+
+	TResult visitOperator(Operator ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/ProgramVisitor.java

@@ -0,0 +1,9 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Program;
+
+public interface ProgramVisitor<TArg, TResult> {
+
+	TResult visitProgram(Program ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/RecordAggregateVisitor.java

@@ -0,0 +1,12 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Aggregates.MultipleRecordAggregate;
+import Triangle.AbstractSyntaxTrees.Aggregates.SingleRecordAggregate;
+
+public interface RecordAggregateVisitor<TArg, TResult> {
+
+	TResult visitMultipleRecordAggregate(MultipleRecordAggregate ast, TArg arg);
+
+	TResult visitSingleRecordAggregate(SingleRecordAggregate ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/TypeDenoterVisitor.java

@@ -0,0 +1,30 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Types.AnyTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.ArrayTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.BoolTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.CharTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.ErrorTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.IntTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.RecordTypeDenoter;
+import Triangle.AbstractSyntaxTrees.Types.SimpleTypeDenoter;
+
+public interface TypeDenoterVisitor<TArg, TResult> extends FieldTypeDenoterVisitor<TArg, TResult> {
+
+	TResult visitAnyTypeDenoter(AnyTypeDenoter ast, TArg arg);
+
+	TResult visitArrayTypeDenoter(ArrayTypeDenoter ast, TArg arg);
+
+	TResult visitBoolTypeDenoter(BoolTypeDenoter ast, TArg arg);
+
+	TResult visitCharTypeDenoter(CharTypeDenoter ast, TArg arg);
+
+	TResult visitErrorTypeDenoter(ErrorTypeDenoter ast, TArg arg);
+
+	TResult visitSimpleTypeDenoter(SimpleTypeDenoter ast, TArg arg);
+
+	TResult visitIntTypeDenoter(IntTypeDenoter ast, TArg arg);
+
+	TResult visitRecordTypeDenoter(RecordTypeDenoter ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Visitors/VnameVisitor.java

@@ -0,0 +1,15 @@
+package Triangle.AbstractSyntaxTrees.Visitors;
+
+import Triangle.AbstractSyntaxTrees.Vnames.DotVname;
+import Triangle.AbstractSyntaxTrees.Vnames.SimpleVname;
+import Triangle.AbstractSyntaxTrees.Vnames.SubscriptVname;
+
+public interface VnameVisitor<TArg, TResult> {
+
+	TResult visitDotVname(DotVname ast, TArg arg);
+
+	TResult visitSimpleVname(SimpleVname ast, TArg arg);
+
+	TResult visitSubscriptVname(SubscriptVname ast, TArg arg);
+
+}

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Vnames/DotVname.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Vnames;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.VnameVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class DotVname extends Vname {
@@ -24,11 +26,10 @@ public class DotVname extends Vname {
 		I = iAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitDotVname(this, o);
+	public <TArg, TResult> TResult visit(VnameVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitDotVname(this, arg);
 	}
 
-	public Identifier I;
-	public Vname V;
+	public final Identifier I;
+	public final Vname V;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Vnames/SimpleVname.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Vnames;
 
+import Triangle.AbstractSyntaxTrees.Terminals.Identifier;
+import Triangle.AbstractSyntaxTrees.Visitors.VnameVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SimpleVname extends Vname {
@@ -23,10 +25,9 @@ public class SimpleVname extends Vname {
 		I = iAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSimpleVname(this, o);
+	public <TArg, TResult> TResult visit(VnameVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSimpleVname(this, arg);
 	}
 
-	public Identifier I;
+	public final Identifier I;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Vnames/SubscriptVname.java

@@ -12,8 +12,10 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Vnames;
 
+import Triangle.AbstractSyntaxTrees.Expressions.Expression;
+import Triangle.AbstractSyntaxTrees.Visitors.VnameVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
 public class SubscriptVname extends Vname {
@@ -24,11 +26,10 @@ public class SubscriptVname extends Vname {
 		E = eAST;
 	}
 
-	@Override
-	public Object visit(Visitor v, Object o) {
-		return v.visitSubscriptVname(this, o);
+	public <TArg, TResult> TResult visit(VnameVisitor<TArg, TResult> v, TArg arg) {
+		return v.visitSubscriptVname(this, arg);
 	}
 
-	public Expression E;
-	public Vname V;
+	public final Expression E;
+	public final Vname V;
 }

Triangle.Compiler/src/main/java/Triangle/AbstractSyntaxTrees/Vnames/Vname.java

@@ -12,11 +12,14 @@
  * of the authors.
  */
 
-package Triangle.AbstractSyntaxTrees;
+package Triangle.AbstractSyntaxTrees.Vnames;
 
+import Triangle.AbstractSyntaxTrees.AbstractSyntaxTree;
+import Triangle.AbstractSyntaxTrees.Types.TypeDenoter;
+import Triangle.AbstractSyntaxTrees.Visitors.VnameVisitor;
 import Triangle.SyntacticAnalyzer.SourcePosition;
 
-public abstract class Vname extends AST {
+public abstract class Vname extends AbstractSyntaxTree {
 
 	public Vname(SourcePosition position) {
 		super(position);
@@ -27,4 +30,10 @@ public abstract class Vname extends AST {
 	public boolean variable, indexed;
 	public int offset;
 	public TypeDenoter type;
+
+	public abstract <TArg, TResult> TResult visit(VnameVisitor<TArg, TResult> visitor, TArg arg);
+
+	public <TArg, TResult> TResult visit(VnameVisitor<TArg, TResult> visitor) {
+		return visit(visitor, null);
+	}
 }