merge

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

@@ -21,6 +21,8 @@ import java.io.IOException;
 
 public class Interpreter {
 
+	static long startTimeNanos = 0;
+	
 	static String objectName;
 
 	// DATA STORE
@@ -183,6 +185,7 @@ public class Interpreter {
 			break;
 		case halted:
 			System.out.println("Program has halted normally.");
+			System.out.println("Total execution time (ns): " + (System.nanoTime() - startTimeNanos));
 			break;
 		case failedDataStoreFull:
 			System.out.println("Program has failed due to exhaustion of Data Store.");
@@ -634,6 +637,7 @@ public class Interpreter {
 
 		loadObjectProgram(objectName);
 		if (CT != CB) {
+			startTimeNanos = System.nanoTime();
 			interpretProgram();
 			showStatus();
 		}

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

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

Triangle.Compiler/src/main/java/triangle/Compiler.java

@@ -18,6 +18,7 @@ import triangle.abstractSyntaxTrees.Program;
 import triangle.codeGenerator.Emitter;
 import triangle.codeGenerator.Encoder;
 import triangle.contextualAnalyzer.Checker;
+import triangle.optimiser.ConstantFolder;
 import triangle.syntacticAnalyzer.Parser;
 import triangle.syntacticAnalyzer.Scanner;
 import triangle.syntacticAnalyzer.SourceFile;
@@ -35,6 +36,7 @@ public class Compiler {
 	static String objectName = "obj.tam";
 	
 	static boolean showTree = false;
+	static boolean folding = false;
 
 	private static Scanner scanner;
 	private static Parser parser;
@@ -91,6 +93,10 @@ public class Compiler {
 			if (showingAST) {
 				drawer.draw(theAST);
 			}
+			if (folding) {
+				theAST.visit(new ConstantFolder());
+			}
+			
 			if (reporter.getNumErrors() == 0) {
 				System.out.println("Code Generation ...");
 				encoder.encodeRun(theAST, showingTable); // 3rd pass
@@ -116,7 +122,7 @@ public class Compiler {
 	public static void main(String[] args) {
 
 		if (args.length < 1) {
-			System.out.println("Usage: tc filename [-o=outputfilename] [tree]");
+			System.out.println("Usage: tc filename [-o=outputfilename] [tree] [folding]");
 			System.exit(1);
 		}
 		
@@ -138,6 +144,8 @@ public class Compiler {
 				showTree = true;
 			} else if (sl.startsWith("-o=")) {
 				objectName = s.substring(3);
+			} else if (sl.equals("folding")) {
+				folding = true;
 			}
 		}
 	}

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/actuals/ConstActualParameter.java

@@ -29,5 +29,5 @@ public class ConstActualParameter extends ActualParameter {
 		return v.visitConstActualParameter(this, arg);
 	}
 
-	public final Expression E;
+	public Expression E;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/aggregates/MultipleArrayAggregate.java

@@ -30,6 +30,6 @@ public class MultipleArrayAggregate extends ArrayAggregate {
 		return v.visitMultipleArrayAggregate(this, arg);
 	}
 
-	public final Expression E;
+	public Expression E;
 	public final ArrayAggregate AA;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/aggregates/MultipleRecordAggregate.java

@@ -33,6 +33,6 @@ public class MultipleRecordAggregate extends RecordAggregate {
 	}
 
 	public final Identifier I;
-	public final Expression E;
+	public Expression E;
 	public final RecordAggregate RA;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/aggregates/SingleArrayAggregate.java

@@ -29,5 +29,5 @@ public class SingleArrayAggregate extends ArrayAggregate {
 		return v.visitSingleArrayAggregate(this, arg);
 	}
 
-	public final Expression E;
+	public Expression E;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/aggregates/SingleRecordAggregate.java

@@ -32,5 +32,5 @@ public class SingleRecordAggregate extends RecordAggregate {
 	}
 
 	public final Identifier I;
-	public final Expression E;
+	public Expression E;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/commands/AssignCommand.java

@@ -32,5 +32,5 @@ public class AssignCommand extends Command {
 	}
 
 	public final Vname V;
-	public final Expression E;
+	public Expression E;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/commands/IfCommand.java

@@ -31,6 +31,6 @@ public class IfCommand extends Command {
 		return v.visitIfCommand(this, arg);
 	}
 
-	public final Expression E;
+	public Expression E;
 	public final Command C1, C2;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/commands/WhileCommand.java

@@ -30,6 +30,6 @@ public class WhileCommand extends Command {
 		return v.visitWhileCommand(this, arg);
 	}
 
-	public final Expression E;
+	public Expression E;
 	public final Command C;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/declarations/ConstDeclaration.java

@@ -38,5 +38,5 @@ public class ConstDeclaration extends Declaration implements ConstantDeclaration
 	}
 
 	public final Identifier I;
-	public final Expression E;
+	public Expression E;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/declarations/FuncDeclaration.java

@@ -49,5 +49,5 @@ public class FuncDeclaration extends Declaration implements FunctionDeclaration
 	public final Identifier I;
 	public final FormalParameterSequence FPS;
 	public TypeDenoter T;
-	public final Expression E;
+	public Expression E;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/expressions/BinaryExpression.java

@@ -31,6 +31,7 @@ public class BinaryExpression extends Expression {
 		return v.visitBinaryExpression(this, arg);
 	}
 
-	public final Expression E1, E2;
+	public Expression E1;
+	public Expression E2;
 	public final Operator O;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/expressions/IfExpression.java

@@ -30,5 +30,7 @@ public class IfExpression extends Expression {
 		return v.visitIfExpression(this, arg);
 	}
 
-	public final Expression E1, E2, E3;
+	public Expression E1;
+	public Expression E2;
+	public Expression E3;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/expressions/LetExpression.java

@@ -31,5 +31,5 @@ public class LetExpression extends Expression {
 	}
 
 	public final Declaration D;
-	public final Expression E;
+	public Expression E;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/expressions/UnaryExpression.java

@@ -30,6 +30,6 @@ public class UnaryExpression extends Expression {
 		return v.visitUnaryExpression(this, arg);
 	}
 
-	public final Expression E;
+	public Expression E;
 	public final Operator O;
 }

Triangle.Compiler/src/main/java/triangle/abstractSyntaxTrees/vnames/SubscriptVname.java

@@ -30,6 +30,6 @@ public class SubscriptVname extends Vname {
 		return v.visitSubscriptVname(this, arg);
 	}
 
-	public final Expression E;
+	public Expression E;
 	public final Vname V;
 }

Triangle.Compiler/src/main/java/triangle/codeGenerator/Encoder.java

@@ -755,10 +755,9 @@ public final class Encoder implements ActualParameterVisitor<Frame, Integer>,
 	public static void writeTableDetails(AbstractSyntaxTree ast) {
 	}
 
-	// Generates code to fetch the value of a named constant or variable
-	// and push it on to the stack.
-	// currentLevel is the routine level where the vname occurs.
-	// frameSize is the anticipated size of the local stack frame when
+	// Generates code to pop the top off the stack
+	// and store the value in a named constant or variable
+	// frame the local stack frame when
 	// the constant or variable is fetched at run-time.
 	// valSize is the size of the constant or variable's value.
 

Triangle.Compiler/src/main/java/triangle/optimiser/ConstantFolder.java

@@ -0,0 +1,601 @@
+package triangle.optimiser;
+
+import triangle.StdEnvironment;
+import triangle.abstractSyntaxTrees.AbstractSyntaxTree;
+import triangle.abstractSyntaxTrees.Program;
+import triangle.abstractSyntaxTrees.actuals.ConstActualParameter;
+import triangle.abstractSyntaxTrees.actuals.EmptyActualParameterSequence;
+import triangle.abstractSyntaxTrees.actuals.FuncActualParameter;
+import triangle.abstractSyntaxTrees.actuals.MultipleActualParameterSequence;
+import triangle.abstractSyntaxTrees.actuals.ProcActualParameter;
+import triangle.abstractSyntaxTrees.actuals.SingleActualParameterSequence;
+import triangle.abstractSyntaxTrees.actuals.VarActualParameter;
+import triangle.abstractSyntaxTrees.aggregates.MultipleArrayAggregate;
+import triangle.abstractSyntaxTrees.aggregates.MultipleRecordAggregate;
+import triangle.abstractSyntaxTrees.aggregates.SingleArrayAggregate;
+import triangle.abstractSyntaxTrees.aggregates.SingleRecordAggregate;
+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.RepeatCommand;
+import triangle.abstractSyntaxTrees.commands.SequentialCommand;
+import triangle.abstractSyntaxTrees.commands.WhileCommand;
+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.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.Expression;
+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;
+import triangle.abstractSyntaxTrees.formals.ConstFormalParameter;
+import triangle.abstractSyntaxTrees.formals.EmptyFormalParameterSequence;
+import triangle.abstractSyntaxTrees.formals.FuncFormalParameter;
+import triangle.abstractSyntaxTrees.formals.MultipleFormalParameterSequence;
+import triangle.abstractSyntaxTrees.formals.ProcFormalParameter;
+import triangle.abstractSyntaxTrees.formals.SingleFormalParameterSequence;
+import triangle.abstractSyntaxTrees.formals.VarFormalParameter;
+import triangle.abstractSyntaxTrees.terminals.CharacterLiteral;
+import triangle.abstractSyntaxTrees.terminals.Identifier;
+import triangle.abstractSyntaxTrees.terminals.IntegerLiteral;
+import triangle.abstractSyntaxTrees.terminals.Operator;
+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.MultipleFieldTypeDenoter;
+import triangle.abstractSyntaxTrees.types.RecordTypeDenoter;
+import triangle.abstractSyntaxTrees.types.SimpleTypeDenoter;
+import triangle.abstractSyntaxTrees.types.SingleFieldTypeDenoter;
+import triangle.abstractSyntaxTrees.types.TypeDeclaration;
+import triangle.abstractSyntaxTrees.visitors.ActualParameterSequenceVisitor;
+import triangle.abstractSyntaxTrees.visitors.ActualParameterVisitor;
+import triangle.abstractSyntaxTrees.visitors.ArrayAggregateVisitor;
+import triangle.abstractSyntaxTrees.visitors.CommandVisitor;
+import triangle.abstractSyntaxTrees.visitors.DeclarationVisitor;
+import triangle.abstractSyntaxTrees.visitors.ExpressionVisitor;
+import triangle.abstractSyntaxTrees.visitors.FormalParameterSequenceVisitor;
+import triangle.abstractSyntaxTrees.visitors.IdentifierVisitor;
+import triangle.abstractSyntaxTrees.visitors.LiteralVisitor;
+import triangle.abstractSyntaxTrees.visitors.OperatorVisitor;
+import triangle.abstractSyntaxTrees.visitors.ProgramVisitor;
+import triangle.abstractSyntaxTrees.visitors.RecordAggregateVisitor;
+import triangle.abstractSyntaxTrees.visitors.TypeDenoterVisitor;
+import triangle.abstractSyntaxTrees.visitors.VnameVisitor;
+import triangle.abstractSyntaxTrees.vnames.DotVname;
+import triangle.abstractSyntaxTrees.vnames.SimpleVname;
+import triangle.abstractSyntaxTrees.vnames.SubscriptVname;
+import triangle.codeGenerator.entities.RuntimeEntity;
+
+public class ConstantFolder implements ActualParameterVisitor<Void, AbstractSyntaxTree>,
+		ActualParameterSequenceVisitor<Void, AbstractSyntaxTree>, ArrayAggregateVisitor<Void, AbstractSyntaxTree>,
+		CommandVisitor<Void, AbstractSyntaxTree>, DeclarationVisitor<Void, AbstractSyntaxTree>,
+		ExpressionVisitor<Void, AbstractSyntaxTree>, FormalParameterSequenceVisitor<Void, AbstractSyntaxTree>,
+		IdentifierVisitor<Void, AbstractSyntaxTree>, LiteralVisitor<Void, AbstractSyntaxTree>,
+		OperatorVisitor<Void, AbstractSyntaxTree>, ProgramVisitor<Void, AbstractSyntaxTree>,
+		RecordAggregateVisitor<Void, AbstractSyntaxTree>, TypeDenoterVisitor<Void, AbstractSyntaxTree>,
+		VnameVisitor<Void, RuntimeEntity> {
+	{
+
+	}
+
+	@Override
+	public AbstractSyntaxTree visitConstFormalParameter(ConstFormalParameter ast, Void arg) {
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitFuncFormalParameter(FuncFormalParameter ast, Void arg) {
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitProcFormalParameter(ProcFormalParameter ast, Void arg) {
+		ast.I.visit(this);
+		ast.FPS.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitVarFormalParameter(VarFormalParameter ast, Void arg) {
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitMultipleFieldTypeDenoter(MultipleFieldTypeDenoter ast, Void arg) {
+		ast.FT.visit(this);
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSingleFieldTypeDenoter(SingleFieldTypeDenoter ast, Void arg) {
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public RuntimeEntity visitDotVname(DotVname ast, Void arg) {
+		ast.I.visit(this);
+		ast.V.visit(this);
+		return null;
+	}
+
+	@Override
+	public RuntimeEntity visitSimpleVname(SimpleVname ast, Void arg) {
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public RuntimeEntity visitSubscriptVname(SubscriptVname ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		ast.V.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitAnyTypeDenoter(AnyTypeDenoter ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitArrayTypeDenoter(ArrayTypeDenoter ast, Void arg) {
+		ast.IL.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitBoolTypeDenoter(BoolTypeDenoter ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitCharTypeDenoter(CharTypeDenoter ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitErrorTypeDenoter(ErrorTypeDenoter ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSimpleTypeDenoter(SimpleTypeDenoter ast, Void arg) {
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitIntTypeDenoter(IntTypeDenoter ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitRecordTypeDenoter(RecordTypeDenoter ast, Void arg) {
+		ast.FT.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitMultipleRecordAggregate(MultipleRecordAggregate ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		ast.I.visit(this);
+		ast.RA.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSingleRecordAggregate(SingleRecordAggregate ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitProgram(Program ast, Void arg) {
+		ast.C.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitOperator(Operator ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitCharacterLiteral(CharacterLiteral ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitIntegerLiteral(IntegerLiteral ast, Void arg) {
+		return ast;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitIdentifier(Identifier ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitEmptyFormalParameterSequence(EmptyFormalParameterSequence ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitMultipleFormalParameterSequence(MultipleFormalParameterSequence ast, Void arg) {
+		ast.FP.visit(this);
+		ast.FPS.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSingleFormalParameterSequence(SingleFormalParameterSequence ast, Void arg) {
+		ast.FP.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitArrayExpression(ArrayExpression ast, Void arg) {
+		ast.AA.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitBinaryExpression(BinaryExpression ast, Void arg) {
+		AbstractSyntaxTree replacement1 = ast.E1.visit(this);
+		AbstractSyntaxTree replacement2 = ast.E2.visit(this);
+		ast.O.visit(this);
+
+		// if visiting a child node returns something, it's either the original constant
+		// (IntegerLiteral) or a folded version replacing the expression at that child
+		// node
+		// If both child nodes are not null; return a folded version of this
+		// BinaryExpression
+		// Otherwise, at least one child node isn't constant (foldable) so just replace
+		// the
+		// foldable child nodes with their folded equivalent and return null
+		if (replacement1 != null && replacement2 != null) {
+			return foldBinaryExpression(replacement1, replacement2, ast.O);
+		} else if (replacement1 != null) {
+			ast.E1 = (Expression) replacement1;
+		} else if (replacement2 != null) {
+			ast.E2 = (Expression) replacement2;
+		}
+
+		// if we get here, we can't fold any higher than this level
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitCallExpression(CallExpression ast, Void arg) {
+		ast.APS.visit(this);
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitCharacterExpression(CharacterExpression ast, Void arg) {
+		ast.CL.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitEmptyExpression(EmptyExpression ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitIfExpression(IfExpression ast, Void arg) {
+		AbstractSyntaxTree replacement1 = ast.E1.visit(this);
+		if (replacement1 != null) {
+			ast.E1 = (Expression) replacement1;
+		}
+		AbstractSyntaxTree replacement2 = ast.E2.visit(this);
+		if (replacement2 != null) {
+			ast.E2 = (Expression) replacement2;
+		}
+		AbstractSyntaxTree replacement3 = ast.E3.visit(this);
+		if (replacement3 != null) {
+			ast.E3 = (Expression) replacement3;
+		}
+
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitIntegerExpression(IntegerExpression ast, Void arg) {
+		return ast;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitLetExpression(LetExpression ast, Void arg) {
+		ast.D.visit(this);
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitRecordExpression(RecordExpression ast, Void arg) {
+		ast.RA.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitUnaryExpression(UnaryExpression ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+
+		ast.O.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitVnameExpression(VnameExpression ast, Void arg) {
+		ast.V.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitBinaryOperatorDeclaration(BinaryOperatorDeclaration ast, Void arg) {
+		ast.ARG1.visit(this);
+		ast.ARG2.visit(this);
+		ast.O.visit(this);
+		ast.RES.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitConstDeclaration(ConstDeclaration ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitFuncDeclaration(FuncDeclaration ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		ast.FPS.visit(this);
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitProcDeclaration(ProcDeclaration ast, Void arg) {
+		ast.C.visit(this);
+		ast.FPS.visit(this);
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSequentialDeclaration(SequentialDeclaration ast, Void arg) {
+		ast.D1.visit(this);
+		ast.D2.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitTypeDeclaration(TypeDeclaration ast, Void arg) {
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitUnaryOperatorDeclaration(UnaryOperatorDeclaration ast, Void arg) {
+		ast.ARG.visit(this);
+		ast.O.visit(this);
+		ast.RES.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitVarDeclaration(VarDeclaration ast, Void arg) {
+		ast.I.visit(this);
+		ast.T.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitAssignCommand(AssignCommand ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		ast.V.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitCallCommand(CallCommand ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitEmptyCommand(EmptyCommand ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitIfCommand(IfCommand ast, Void arg) {
+		ast.C1.visit(this);
+		ast.C2.visit(this);
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitLetCommand(LetCommand ast, Void arg) {
+		ast.C.visit(this);
+		ast.D.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSequentialCommand(SequentialCommand ast, Void arg) {
+		ast.C1.visit(this);
+		ast.C2.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitWhileCommand(WhileCommand ast, Void arg) {
+		ast.C.visit(this);
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		return null;
+	}
+
+	// TODO uncomment if you've implemented the repeat command
+//	@Override
+//	public AbstractSyntaxTree visitRepeatCommand(RepeatCommand ast, Void arg) {
+//		ast.C.visit(this);
+//		AbstractSyntaxTree replacement = ast.E.visit(this);
+//		if (replacement != null) {
+//			ast.E = (Expression) replacement;
+//		}
+//		return null;
+//	}
+
+	@Override
+	public AbstractSyntaxTree visitMultipleArrayAggregate(MultipleArrayAggregate ast, Void arg) {
+		ast.AA.visit(this);
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSingleArrayAggregate(SingleArrayAggregate ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitEmptyActualParameterSequence(EmptyActualParameterSequence ast, Void arg) {
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitMultipleActualParameterSequence(MultipleActualParameterSequence ast, Void arg) {
+		ast.AP.visit(this);
+		ast.APS.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitSingleActualParameterSequence(SingleActualParameterSequence ast, Void arg) {
+		ast.AP.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitConstActualParameter(ConstActualParameter ast, Void arg) {
+		AbstractSyntaxTree replacement = ast.E.visit(this);
+		if (replacement != null) {
+			ast.E = (Expression) replacement;
+		}
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitFuncActualParameter(FuncActualParameter ast, Void arg) {
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitProcActualParameter(ProcActualParameter ast, Void arg) {
+		ast.I.visit(this);
+		return null;
+	}
+
+	@Override
+	public AbstractSyntaxTree visitVarActualParameter(VarActualParameter ast, Void arg) {
+		ast.V.visit(this);
+		return null;
+	}
+
+	public AbstractSyntaxTree foldBinaryExpression(AbstractSyntaxTree node1, AbstractSyntaxTree node2, Operator o) {
+		// the only case we know how to deal with for now is two IntegerExpressions
+		if ((node1 instanceof IntegerExpression) && (node2 instanceof IntegerExpression)) {
+			int int1 = (Integer.parseInt(((IntegerExpression) node1).IL.spelling));
+			int int2 = (Integer.parseInt(((IntegerExpression) node2).IL.spelling));
+			Object foldedValue = null;
+			
+			if (o.decl == StdEnvironment.addDecl) {
+				foldedValue = int1 + int2;
+			}
+
+			if (foldedValue instanceof Integer) {
+				IntegerLiteral il = new IntegerLiteral(foldedValue.toString(), node1.getPosition());
+				IntegerExpression ie = new IntegerExpression(il, node1.getPosition());
+				ie.type = StdEnvironment.integerType;
+				return ie;
+			} else if (foldedValue instanceof Boolean) {
+				/* currently not handled! */
+			}
+		}
+
+		// any unhandled situation (i.e., not foldable) is ignored
+		return null;
+	}
+
+}

programs/bardemo.tri

@@ -9,12 +9,19 @@ in
         b := 2;
         
         putint(a);
+<<<<<<< HEAD
         puteol();
+=======
+	puteol();
+>>>>>>> ce307a11a6c71de9c69bd0a4c91205bb6437f6e9
         putint(b);
         puteol();
         putint(|a);
         puteol();
         putint(|b);
         puteol()
+<<<<<<< HEAD
 
+=======
+>>>>>>> ce307a11a6c71de9c69bd0a4c91205bb6437f6e9
     end

programs/increment.tri

@@ -0,0 +1,14 @@
+! this won't compile without implementing the bonus material in Practical 3
+
+let
+    var a: Integer
+in
+begin
+    getint(var a);
+    a++;
+    putint(a);
+    puteol();
+    a++;
+    putint(a);
+    puteol();
+end

programs/repeatuntil.tri

@@ -10,5 +10,5 @@ begin
     put('a');
     a := a + 1;
   end
-  until a < 5
+  until a >= 5
 end

programs/while-longloop.tri

@@ -0,0 +1,22 @@
+let
+  var a : Integer;
+  var b : Integer;
+  var c : Integer
+in
+begin
+  put('1');
+  puteol();
+  a := 0;
+  while a < 5000 do
+  begin
+    b := 0;
+    while b < 3000 do
+    begin
+      c := c + a;
+      c := c / (1 + b);
+      b := b + 1;
+    end;
+    a := a + 1;
+  end;
+  putint(c);
+end