Switch to generic visitor pattern.

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 {
@@ -23,19 +24,19 @@ 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);
+	}
 }

Triangle.Compiler/src/main/java/Triangle/CodeGenerator/Emitter.java

@@ -0,0 +1,120 @@
+package Triangle.CodeGenerator;
+
+import java.io.DataOutputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+import Triangle.ErrorReporter;
+import Triangle.AbstractMachine.Instruction;
+import Triangle.AbstractMachine.Machine;
+import Triangle.AbstractMachine.OpCode;
+import Triangle.AbstractMachine.Primitive;
+import Triangle.AbstractMachine.Register;
+
+public class Emitter {
+
+	// OBJECT CODE
+
+	// Implementation notes:
+	// Object code is generated directly into the TAM Code Store, starting at
+	// CB.
+	// The address of the next instruction is held in nextInstrAddr.
+
+	ErrorReporter errorReporter;
+
+	int nextInstrAddr;
+
+	public Emitter(ErrorReporter errorReporter) {
+		this.errorReporter = errorReporter;
+		nextInstrAddr = Machine.CB;
+	}
+
+	public int getNextInstrAddr() {
+		return nextInstrAddr;
+	}
+
+	public int emit(OpCode op) {
+		return emit(op, 0, Register.CB, 0);
+	}
+
+	public int emit(OpCode op, int operand) {
+		return emit(op, 0, Register.CB, operand);
+	}
+
+	public int emit(OpCode op, int length, int operand) {
+		return emit(op, length, Register.CB, operand);
+	}
+
+	public int emit(OpCode op, Register staticRegister, Register register, int operand) {
+		return emit(op, staticRegister.ordinal(), register, operand);
+	}
+
+	public int emit(OpCode op, Register register, int operand) {
+		return emit(op, 0, register, operand);
+	}
+
+	public int emit(OpCode op, Register register) {
+		return emit(op, 0, register, 0);
+	}
+
+	public int emit(OpCode op, int length, Register register) {
+		return emit(op, length, register, 0);
+	}
+
+	public int emit(OpCode op, Register register, Primitive primitive) {
+		return emit(op, 0, register, primitive.ordinal());
+	}
+
+	/**
+	 * Appends an instruction, with the given fields, to the object code.
+	 *
+	 * @param op       the opcode
+	 * @param length   the length field
+	 * @param register the register field
+	 * @param operand  the operand field
+	 * @return the code address of the new instruction
+	 **/
+	public int emit(OpCode op, int length, Register register, int operand) {
+
+		if (length > 255) {
+			errorReporter.reportRestriction("length of operand can't exceed 255 words");
+			length = 255; // to allow code generation to continue
+		}
+
+		var nextInstr = new Instruction(op, register, length, operand);
+
+		var currentInstrAddr = nextInstrAddr;
+		if (nextInstrAddr == Machine.PB) {
+			errorReporter.reportRestriction("too many instructions for code segment");
+		} else {
+			Machine.code[nextInstrAddr++] = nextInstr;
+		}
+		return currentInstrAddr;
+
+	}
+
+	// Patches the d-field of the instruction at address addr with the next
+	// instruction address.
+	public void patch(int addr) {
+		Machine.code[addr].setOperand(nextInstrAddr);
+	}
+
+	/**
+	 * Saves the object program in the given object file.
+	 * 
+	 * @param objectFile the object file
+	 */
+	public void saveObjectProgram(String objectFileName) {
+		try (var objectFile = new FileOutputStream(objectFileName)) {
+			var objectStream = new DataOutputStream(objectFile);
+			for (var addr = Machine.CB; addr < nextInstrAddr; addr++) {
+				Machine.code[addr].write(objectStream);
+			}
+		} catch (FileNotFoundException fnfe) {
+			System.err.println("Error opening object file: " + fnfe);
+		} catch (IOException ioe) {
+			System.err.println("Error writing object file: " + ioe);
+		}
+	}
+}

Triangle.Compiler/src/main/java/Triangle/CodeGenerator/Entities/AddressableEntity.java

@@ -0,0 +1,29 @@
+package Triangle.CodeGenerator.Entities;
+
+import Triangle.AbstractSyntaxTrees.Vnames.Vname;
+import Triangle.CodeGenerator.Emitter;
+import Triangle.CodeGenerator.Frame;
+
+public abstract class AddressableEntity extends RuntimeEntity implements FetchableEntity {
+
+	protected final ObjectAddress address;
+
+	protected AddressableEntity(int size, int level, int displacement) {
+		super(size);
+		address = new ObjectAddress(level, displacement);
+	}
+
+	protected AddressableEntity(int size, Frame frame) {
+		this(size, frame.getLevel(), frame.getSize());
+	}
+
+	public ObjectAddress getAddress() {
+		return address;
+	}
+
+	public abstract void encodeStore(Emitter emitter, Frame frame, int size, Vname vname);
+
+	public abstract void encodeFetchAddress(Emitter emitter, Frame frame, Vname vname);
+
+	public abstract void encodeFetch(Emitter emitter, Frame frame, int size, Vname vname);
+}

Triangle.Compiler/src/main/java/Triangle/CodeGenerator/Entities/EqualityRoutine.java

@@ -0,0 +1,46 @@
+/*
+ * @(#)EqualityRoutine.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.CodeGenerator.Entities;
+
+import Triangle.AbstractMachine.OpCode;
+import Triangle.AbstractMachine.Primitive;
+import Triangle.AbstractMachine.Register;
+import Triangle.CodeGenerator.Emitter;
+import Triangle.CodeGenerator.Frame;
+
+public class EqualityRoutine extends RuntimeEntity implements RoutineEntity {
+
+	private final Primitive primitive;
+
+	public EqualityRoutine(int size, Primitive primitive) {
+		super(size);
+		this.primitive = primitive;
+	}
+
+	public final Primitive getPrimitive() {
+		return primitive;
+	}
+
+	public void encodeCall(Emitter emitter, Frame frame) {
+		emitter.emit(OpCode.LOADL, frame.getSize() / 2);
+		emitter.emit(OpCode.CALL, Register.PB, primitive);
+	}
+
+	public void encodeFetch(Emitter emitter, Frame frame) {
+		emitter.emit(OpCode.LOADA, 0, Register.SB, 0);
+		emitter.emit(OpCode.LOADA, Register.PB, primitive);
+	}
+
+}

Triangle.Compiler/src/main/java/Triangle/CodeGenerator/Entities/FetchableEntity.java

@@ -0,0 +1,11 @@
+package Triangle.CodeGenerator.Entities;
+
+import Triangle.AbstractSyntaxTrees.Vnames.Vname;
+import Triangle.CodeGenerator.Emitter;
+import Triangle.CodeGenerator.Frame;
+
+public interface FetchableEntity {
+
+    void encodeFetch(Emitter emitter, Frame frame, int size, Vname vname);
+
+}

Triangle.Compiler/src/main/java/Triangle/CodeGenerator/Entities/Field.java

@@ -12,20 +12,18 @@
  * of the authors.
  */
 
-package Triangle.CodeGenerator;
+package Triangle.CodeGenerator.Entities;
 
 public class Field extends RuntimeEntity {
 
-	public Field() {
-		super();
-		fieldOffset = 0;
-	}
+	private final int fieldOffset;
 
 	public Field(int size, int fieldOffset) {
 		super(size);
 		this.fieldOffset = fieldOffset;
 	}
 
-	public int fieldOffset;
-
+	public final int getFieldOffset() {
+		return fieldOffset;
+	}
 }

Triangle.Compiler/src/main/java/Triangle/CodeGenerator/Entities/KnownAddress.java

@@ -0,0 +1,62 @@
+/*
+ * @(#)KnownAddress.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.CodeGenerator.Entities;
+
+import Triangle.AbstractMachine.OpCode;
+import Triangle.AbstractMachine.Primitive;
+import Triangle.AbstractMachine.Register;
+import Triangle.AbstractSyntaxTrees.Vnames.Vname;
+import Triangle.CodeGenerator.Emitter;
+import Triangle.CodeGenerator.Frame;
+
+public class KnownAddress extends AddressableEntity {
+
+	public KnownAddress(int size, int level, int displacement) {
+		super(size, level, displacement);
+	}
+
+	public KnownAddress(int size, Frame frame) {
+		super(size, frame);
+	}
+
+	public void encodeStore(Emitter emitter, Frame frame, int size, Vname vname) {
+		if (vname.indexed) {
+			emitter.emit(OpCode.LOADA, 0, frame.getDisplayRegister(address), address.getDisplacement() + vname.offset);
+			emitter.emit(OpCode.CALL, Register.PB, Primitive.ADD);
+			emitter.emit(OpCode.STOREI, size, 0);
+		} else {
+			emitter.emit(OpCode.STORE, size, frame.getDisplayRegister(address),
+					address.getDisplacement() + vname.offset);
+		}
+	}
+
+	public void encodeFetch(Emitter emitter, Frame frame, int size, Vname vname) {
+		if (vname.indexed) {
+			emitter.emit(OpCode.LOADA, 0, frame.getDisplayRegister(address), address.getDisplacement() + vname.offset);
+			emitter.emit(OpCode.CALL, Register.PB, Primitive.ADD);
+			emitter.emit(OpCode.LOADI, size, 0);
+		} else {
+			emitter.emit(OpCode.LOAD, size, frame.getDisplayRegister(address),
+					address.getDisplacement() + vname.offset);
+		}
+	}
+
+	public void encodeFetchAddress(Emitter emitter, Frame frame, Vname vname) {
+		emitter.emit(OpCode.LOADA, 0, frame.getDisplayRegister(address), address.getDisplacement() + vname.offset);
+		if (vname.indexed) {
+			emitter.emit(OpCode.CALL, Register.PB, Primitive.ADD);
+		}
+	}
+}