checker.java

The triangle language processor will be consist of a compiler, an interpreter, and a disassembler

    ast.T = (TypeDenoter) ast.T.visit(this, null);
    ast.FT.visit(this, null);
    return ast;
  }

  public Object visitSingleFieldTypeDenoter(SingleFieldTypeDenoter ast, Object o) {
    ast.T = (TypeDenoter) ast.T.visit(this, null);
    return ast;
  }

  // Literals, Identifiers and Operators
  public Object visitCharacterLiteral(CharacterLiteral CL, Object o) {
    return StdEnvironment.charType;
  }

  public Object visitIdentifier(Identifier I, Object o) {
    Declaration binding = idTable.retrieve(I.spelling);
    if (binding != null)
      I.decl = binding;
    return binding;
  }

  public Object visitIntegerLiteral(IntegerLiteral IL, Object o) {
    return StdEnvironment.integerType;
  }

  public Object visitOperator(Operator O, Object o) {
    Declaration binding = idTable.retrieve(O.spelling);
    if (binding != null)
      O.decl = binding;
    return binding;
  }

  // Value-or-variable names

  // Determines the address of a named object (constant or variable).
  // This consists of a base object, to which 0 or more field-selection
  // or array-indexing operations may be applied (if it is a record or
  // array).  As much as possible of the address computation is done at
  // compile-time. Code is generated only when necessary to evaluate
  // index expressions at run-time.
  // currentLevel is the routine level where the v-name occurs.
  // frameSize is the anticipated size of the local stack frame when
  // the object is addressed at run-time.
  // It returns the description of the base object.
  // offset is set to the total of any field offsets (plus any offsets
  // due to index expressions that happen to be literals).
  // indexed is set to true iff there are any index expressions (other
  // than literals). In that case code is generated to compute the
  // offset due to these indexing operations at run-time.

  // Returns the TypeDenoter of the Vname. Does not use the
  // given object.

  public Object visitDotVname(DotVname ast, Object o) {
    ast.type = null;
    TypeDenoter vType = (TypeDenoter) ast.V.visit(this, null);
    ast.variable = ast.V.variable;
    if (! (vType instanceof RecordTypeDenoter))
      reporter.reportError ("record expected here", "", ast.V.position);
    else {
      ast.type = checkFieldIdentifier(((RecordTypeDenoter) vType).FT, ast.I);
      if (ast.type == StdEnvironment.errorType)
        reporter.reportError ("no field \"%\" in this record type",
                              ast.I.spelling, ast.I.position);
    }
    return ast.type;
  }

  public Object visitSimpleVname(SimpleVname ast, Object o) {
    ast.variable = false;
    ast.type = StdEnvironment.errorType;
    Declaration binding = (Declaration) ast.I.visit(this, null);
    if (binding == null)
      reportUndeclared(ast.I);
    else
      if (binding instanceof ConstDeclaration) {
        ast.type = ((ConstDeclaration) binding).E.type;
        ast.variable = false;
      } else if (binding instanceof VarDeclaration) {
        ast.type = ((VarDeclaration) binding).T;
        ast.variable = true;
      } else if (binding instanceof ConstFormalParameter) {
        ast.type = ((ConstFormalParameter) binding).T;
        ast.variable = false;
      } else if (binding instanceof VarFormalParameter) {
        ast.type = ((VarFormalParameter) binding).T;
        ast.variable = true;
      } else
        reporter.reportError ("\"%\" is not a const or var identifier",
                              ast.I.spelling, ast.I.position);
    return ast.type;
  }

  public Object visitSubscriptVname(SubscriptVname ast, Object o) {
    TypeDenoter vType = (TypeDenoter) ast.V.visit(this, null);
    ast.variable = ast.V.variable;
    TypeDenoter eType = (TypeDenoter) ast.E.visit(this, null);
    if (vType != StdEnvironment.errorType) {
      if (! (vType instanceof ArrayTypeDenoter))
        reporter.reportError ("array expected here", "", ast.V.position);
      else {
        if (! eType.equals(StdEnvironment.integerType))
          reporter.reportError ("Integer expression expected here", "",
				ast.E.position);
        ast.type = ((ArrayTypeDenoter) vType).T;
      }
    }
    return ast.type;
  }

  // Programs

  public Object visitProgram(Program ast, Object o) {
    ast.C.visit(this, null);
    return null;
  }

  // Checks whether the source program, represented by its AST, satisfies the
  // language's scope rules and type rules.
  // Also decorates the AST as follows:
  //  (a) Each applied occurrence of an identifier or operator is linked to
  //      the corresponding declaration of that identifier or operator.
  //  (b) Each expression and value-or-variable-name is decorated by its type.
  //  (c) Each type identifier is replaced by the type it denotes.
  // Types are represented by small ASTs.

  public void check(Program ast) {
    ast.visit(this, null);
  }

  /////////////////////////////////////////////////////////////////////////////

  public Checker (ErrorReporter reporter) {
    this.reporter = reporter;
    this.idTable = new IdentificationTable ();
    establishStdEnvironment();
  }

  private IdentificationTable idTable;
  private static SourcePosition dummyPos = new SourcePosition();
  private ErrorReporter reporter;

  // Reports that the identifier or operator used at a leaf of the AST
  // has not been declared.

  private void reportUndeclared (Terminal leaf) {
    reporter.reportError("\"%\" is not declared", leaf.spelling, leaf.position);
  }


  private static TypeDenoter checkFieldIdentifier(FieldTypeDenoter ast, Identifier I) {
    if (ast instanceof MultipleFieldTypeDenoter) {
      MultipleFieldTypeDenoter ft = (MultipleFieldTypeDenoter) ast;
      if (ft.I.spelling.compareTo(I.spelling) == 0) {
        I.decl = ast;
        return ft.T;
      } else {
        return checkFieldIdentifier (ft.FT, I);
      }
    } else if (ast instanceof SingleFieldTypeDenoter) {
      SingleFieldTypeDenoter ft = (SingleFieldTypeDenoter) ast;
      if (ft.I.spelling.compareTo(I.spelling) == 0) {
        I.decl = ast;
        return ft.T;
      }
    }
    return StdEnvironment.errorType;
  }


  // Creates a small AST to represent the "declaration" of a standard
  // type, and enters it in the identification table.

  private TypeDeclaration declareStdType (String id, TypeDenoter typedenoter) {

    TypeDeclaration binding;

    binding = new TypeDeclaration(new Identifier(id, dummyPos), typedenoter, dummyPos);
    idTable.enter(id, binding);
    return binding;
  }

  // Creates a small AST to represent the "declaration" of a standard
  // type, and enters it in the identification table.

  private ConstDeclaration declareStdConst (String id, TypeDenoter constType) {

    IntegerExpression constExpr;
    ConstDeclaration binding;

    // constExpr used only as a placeholder for constType
    constExpr = new IntegerExpression(null, dummyPos);
    constExpr.type = constType;
    binding = new ConstDeclaration(new Identifier(id, dummyPos), constExpr, dummyPos);
    idTable.enter(id, binding);
    return binding;
  }

  // Creates a small AST to represent the "declaration" of a standard
  // type, and enters it in the identification table.

  private ProcDeclaration declareStdProc (String id, FormalParameterSequence fps) {

    ProcDeclaration binding;

    binding = new ProcDeclaration(new Identifier(id, dummyPos), fps,
                                  new EmptyCommand(dummyPos), dummyPos);
    idTable.enter(id, binding);
    return binding;
  }

  // Creates a small AST to represent the "declaration" of a standard
  // type, and enters it in the identification table.

  private FuncDeclaration declareStdFunc (String id, FormalParameterSequence fps,
                                          TypeDenoter resultType) {

    FuncDeclaration binding;

    binding = new FuncDeclaration(new Identifier(id, dummyPos), fps, resultType,
                                  new EmptyExpression(dummyPos), dummyPos);
    idTable.enter(id, binding);
    return binding;
  }

  // Creates a small AST to represent the "declaration" of a
  // unary operator, and enters it in the identification table.
  // This "declaration" summarises the operator's type info.

  private UnaryOperatorDeclaration declareStdUnaryOp
    (String op, TypeDenoter argType, TypeDenoter resultType) {

    UnaryOperatorDeclaration binding;

    binding = new UnaryOperatorDeclaration (new Operator(op, dummyPos),
                                            argType, resultType, dummyPos);
    idTable.enter(op, binding);
    return binding;
  }

  // Creates a small AST to represent the "declaration" of a
  // binary operator, and enters it in the identification table.
  // This "declaration" summarises the operator's type info.

  private BinaryOperatorDeclaration declareStdBinaryOp
    (String op, TypeDenoter arg1Type, TypeDenoter arg2type, TypeDenoter resultType) {

    BinaryOperatorDeclaration binding;

    binding = new BinaryOperatorDeclaration (new Operator(op, dummyPos),
                                             arg1Type, arg2type, resultType, dummyPos);
    idTable.enter(op, binding);
    return binding;
  }

  // Creates small ASTs to represent the standard types.
  // Creates small ASTs to represent "declarations" of standard types,
  // constants, procedures, functions, and operators.
  // Enters these "declarations" in the identification table.

  private final static Identifier dummyI = new Identifier("", dummyPos);

  private void establishStdEnvironment () {

    // idTable.startIdentification();
    StdEnvironment.booleanType = new BoolTypeDenoter(dummyPos);
    StdEnvironment.integerType = new IntTypeDenoter(dummyPos);
    StdEnvironment.charType = new CharTypeDenoter(dummyPos);
    StdEnvironment.anyType = new AnyTypeDenoter(dummyPos);
    StdEnvironment.errorType = new ErrorTypeDenoter(dummyPos);

    StdEnvironment.booleanDecl = declareStdType("Boolean", StdEnvironment.booleanType);
    StdEnvironment.falseDecl = declareStdConst("false", StdEnvironment.booleanType);
    StdEnvironment.trueDecl = declareStdConst("true", StdEnvironment.booleanType);
    StdEnvironment.notDecl = declareStdUnaryOp("\\", StdEnvironment.booleanType, StdEnvironment.booleanType);
    StdEnvironment.andDecl = declareStdBinaryOp("/\\", StdEnvironment.booleanType, StdEnvironment.booleanType, StdEnvironment.booleanType);
    StdEnvironment.orDecl = declareStdBinaryOp("\\/", StdEnvironment.booleanType, StdEnvironment.booleanType, StdEnvironment.booleanType);

    StdEnvironment.integerDecl = declareStdType("Integer", StdEnvironment.integerType);
    StdEnvironment.maxintDecl = declareStdConst("maxint", StdEnvironment.integerType);
    StdEnvironment.addDecl = declareStdBinaryOp("+", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.integerType);
    StdEnvironment.subtractDecl = declareStdBinaryOp("-", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.integerType);
    StdEnvironment.multiplyDecl = declareStdBinaryOp("*", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.integerType);
    StdEnvironment.divideDecl = declareStdBinaryOp("/", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.integerType);
    StdEnvironment.moduloDecl = declareStdBinaryOp("//", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.integerType);
    StdEnvironment.lessDecl = declareStdBinaryOp("<", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.booleanType);
    StdEnvironment.notgreaterDecl = declareStdBinaryOp("<=", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.booleanType);
    StdEnvironment.greaterDecl = declareStdBinaryOp(">", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.booleanType);
    StdEnvironment.notlessDecl = declareStdBinaryOp(">=", StdEnvironment.integerType, StdEnvironment.integerType, StdEnvironment.booleanType);

    StdEnvironment.charDecl = declareStdType("Char", StdEnvironment.charType);
    StdEnvironment.chrDecl = declareStdFunc("chr", new SingleFormalParameterSequence(
                                      new ConstFormalParameter(dummyI, StdEnvironment.integerType, dummyPos), dummyPos), StdEnvironment.charType);
    StdEnvironment.ordDecl = declareStdFunc("ord", new SingleFormalParameterSequence(
                                      new ConstFormalParameter(dummyI, StdEnvironment.charType, dummyPos), dummyPos), StdEnvironment.integerType);
    StdEnvironment.eofDecl = declareStdFunc("eof", new EmptyFormalParameterSequence(dummyPos), StdEnvironment.booleanType);
    StdEnvironment.eolDecl = declareStdFunc("eol", new EmptyFormalParameterSequence(dummyPos), StdEnvironment.booleanType);
    StdEnvironment.getDecl = declareStdProc("get", new SingleFormalParameterSequence(
                                      new VarFormalParameter(dummyI, StdEnvironment.charType, dummyPos), dummyPos));
    StdEnvironment.putDecl = declareStdProc("put", new SingleFormalParameterSequence(
                                      new ConstFormalParameter(dummyI, StdEnvironment.charType, dummyPos), dummyPos));
    StdEnvironment.getintDecl = declareStdProc("getint", new SingleFormalParameterSequence(
                                            new VarFormalParameter(dummyI, StdEnvironment.integerType, dummyPos), dummyPos));
    StdEnvironment.putintDecl = declareStdProc("putint", new SingleFormalParameterSequence(
                                            new ConstFormalParameter(dummyI, StdEnvironment.integerType, dummyPos), dummyPos));
    StdEnvironment.geteolDecl = declareStdProc("geteol", new EmptyFormalParameterSequence(dummyPos));
    StdEnvironment.puteolDecl = declareStdProc("puteol", new EmptyFormalParameterSequence(dummyPos));
    StdEnvironment.equalDecl = declareStdBinaryOp("=", StdEnvironment.anyType, StdEnvironment.anyType, StdEnvironment.booleanType);
    StdEnvironment.unequalDecl = declareStdBinaryOp("\\=", StdEnvironment.anyType, StdEnvironment.anyType, StdEnvironment.booleanType);

  }
}