public override void Visit(ForStmt forStmt)
{
forStmt.StartExpr.Accept(this);
forStmt.EndExpr.Accept(this);
forStmt.LoopVar.Accept(this);
Symbol loopSymbol = SymbolTable.GetSymbol(forStmt.LoopVar.IdentifierName);
for(int i = (int)forStmt.StartExpr.ExprValue; i <= (int)forStmt.EndExpr.ExprValue; i++)
{
loopSymbol.Value = i;
forStmt.Body.Accept(this);
}
}
public void Visit(ForStmt node)
{
Node identifierNameStmt = node.Children [0];
Node startExpr = node.Children [1];
Node endExpr = node.Children [2];
Node statements = node.Children [3];
VisitChildren (startExpr);
int start = Int32.Parse (ValueStack.Pop ().Value);
VisitChildren (endExpr);
int end = Int32.Parse (ValueStack.Pop ().Value);
for (int i = start; i <= end; i++) {
SymbolTable [identifierNameStmt.Name].Value = i.ToString ();
VisitChildren (statements);
}
ValueStack = new Stack<StackValue> (); // don't leave anything to stack after the For-loop
}
public void Visit(ForStmt node)
{
try {
Node identifierNameStmt = node.Children [0];
Node startExpr = node.Children [1];
Node endExpr = node.Children [2];
Node statements = node.Children [3];
if (!SymbolTable.ContainsKey (identifierNameStmt.Name)) {
throw new SemanticError ("Variable " + identifierNameStmt.Name +
" needs to be declared before use", identifierNameStmt.Row,
identifierNameStmt.Column);
} else if (SymbolTable [identifierNameStmt.Name].Type != "Int") {
throw new SemanticError ("Variable " + identifierNameStmt.Name +
" must be of type int to be used in For-statement", identifierNameStmt.Row,
identifierNameStmt.Column);
}
VisitChildren (startExpr);
string type = TypeStack.Pop ();
if (type != "Int") {
throw new SemanticError ("For-range start needs to be int value, not " +
type, startExpr.Row, startExpr.Column);
}
VisitChildren (endExpr);
type = TypeStack.Pop ();
if (type != "Int") {
throw new SemanticError ("For-range end needs to be int value, not " +
type, endExpr.Row, endExpr.Column);
}
VisitChildren (statements);
} catch (SemanticError error) {
Errors.Add (error);
}
TypeStack.Clear (); // clean the stack as there's no use for the type value(s) at this point
}
public override void Visit(ForStmt forStmt)
{
Expression start = forStmt.StartExpr;
Expression end = forStmt.EndExpr;
IdentifierExpr loopvar = forStmt.LoopVar;
start.Accept(this);
end.Accept(this);
loopvar.Accept(this);
if (loopvar.Type != ExprType.IntType)
{
Errors.AddError(String.Format("For loop variable {0} of type {0} illegal at line {1} column {2}.",
loopvar.IdentifierName, loopvar.Type, loopvar.Line, loopvar.Column), ErrorTypes.SemanticError);
}
if (start.Type != ExprType.IntType || end.Type != ExprType.IntType)
{
Errors.AddError(String.Format("For loop expressions must be of type int at line {0} column {1}.",
forStmt.Line, forStmt.Column), ErrorTypes.SemanticError);
}
forStmt.Body.Accept(this);
}
private Statement Stmt()
{
switch ((Token.Types)currentToken.Type) {
case Token.Types.Var:
VarDeclStmt varDeclStmt = new VarDeclStmt ("VarDecl", currentToken.Row, currentToken.Column);
Match (Token.Types.Var);
varDeclStmt.AddChild (IdentifierNameStmt ());
Match (Token.Types.Colon);
varDeclStmt.AddChild (Type ());
if ((Token.Types)currentToken.Type == Token.Types.Assign) {
Match (Token.Types.Assign);
varDeclStmt.AddChild (Expr ());
return varDeclStmt;
} else if ((Token.Types)currentToken.Type == Token.Types.Semicolon) {
return varDeclStmt;
}
throw new SyntaxError ("Expected Assign, got: " + currentToken.Type, currentToken.Row, currentToken.Column);
case Token.Types.Identifier:
AssignmentStmt assignmentStmt = new AssignmentStmt ("AssignmentStmt", currentToken.Row, currentToken.Column);
assignmentStmt.AddChild (IdentifierNameStmt ());
Match (Token.Types.Assign);
assignmentStmt.AddChild (Expr ());
return assignmentStmt;
case Token.Types.For:
ForStmt forStmt = new ForStmt ("ForStmt", currentToken.Row, currentToken.Column);
Match (Token.Types.For);
forStmt.AddChild (IdentifierNameStmt ());
Match (Token.Types.In);
forStmt.AddChild (Expr ());
Match (Token.Types.Range);
forStmt.AddChild (Expr ());
Match (Token.Types.Do);
forStmt.AddChild (Stmts ());
Match (Token.Types.End);
Match (Token.Types.For);
return forStmt;
case Token.Types.Read:
ReadStmt readStmt = new ReadStmt ("ReadStmt", currentToken.Row, currentToken.Column);
Match (Token.Types.Read);
readStmt.AddChild (IdentifierNameStmt ());
return readStmt;
case Token.Types.Print:
PrintStmt printStmt = new PrintStmt ("PrintStmt", currentToken.Row, currentToken.Column);
Match (Token.Types.Print);
printStmt.AddChild (Expr ());
return printStmt;
case Token.Types.Assert:
AssertStmt assertStmt = new AssertStmt ("AssertStmt", currentToken.Row, currentToken.Column);
Match (Token.Types.Assert);
Match (Token.Types.LeftParenthesis);
assertStmt.AddChild (Expr ());
Match (Token.Types.RightParenthesis);
return assertStmt;
default:
throw new SyntaxError ("invalid start symbol for statement " + currentToken.Lexeme,
currentToken.Row, currentToken.Column);
}
}
private Statement ParseStatement()
{
if (Accept(Token.Types.KwVar))
{
DeclarationStmt declaration = new DeclarationStmt(AcceptedToken.Line, AcceptedToken.Column);
Token id = Match(Token.Types.Identifier);
declaration.Identifier = new IdentifierExpr(id.Line, id.Column, id.Content);
Match(Token.Types.Colon);
TypeNode typeNode = ParseType();
declaration.Type = typeNode;
if (Accept(Token.Types.OpAssignment))
{
declaration.AssignmentExpr = ParseExpression();
}
return declaration;
}
else if (Accept(Token.Types.Identifier))
{
AssignmentStmt statement = new AssignmentStmt(AcceptedToken.Line, AcceptedToken.Column);
statement.Identifier = new IdentifierExpr(AcceptedToken.Line, AcceptedToken.Column, AcceptedToken.Content);
Match(Token.Types.OpAssignment);
statement.AssignmentExpr = ParseExpression();
return statement;
}
else if (Accept(Token.Types.KwFor))
{
ForStmt statement = new ForStmt(AcceptedToken.Line, AcceptedToken.Column);
Token idToken = Match(Token.Types.Identifier);
statement.LoopVar = new IdentifierExpr(idToken.Line, idToken.Column, idToken.Content);
Match(Token.Types.KwIn);
statement.StartExpr = ParseExpression();
Match(Token.Types.OpRange);
statement.EndExpr = ParseExpression();
Match(Token.Types.KwDo);
statement.Body = ParseStatements(new StmtList(CurrentToken.Line, CurrentToken.Column));
Match(Token.Types.KwEnd);
Match(Token.Types.KwFor);
return statement;
}
else if (Accept(Token.Types.KwRead))
{
ReadStmt statement = new ReadStmt(AcceptedToken.Line, AcceptedToken.Column);
Token idToken = Match(Token.Types.Identifier);
statement.Variable = new IdentifierExpr(idToken.Line, idToken.Column, idToken.Content);
return statement;
}
else if (Accept(Token.Types.KwPrint))
{
PrintStmt statement = new PrintStmt(AcceptedToken.Line, AcceptedToken.Column);
statement.PrintExpr = ParseExpression();
return statement;
}
else if (Accept(Token.Types.KwAssert))
{
AssertStmt statement = new AssertStmt(AcceptedToken.Line, AcceptedToken.Column);
Match(Token.Types.LParen);
statement.AssertExpr = ParseExpression();
Match(Token.Types.RParen);
return statement;
}
throw new ParserException(String.Format("Expected statement, got {0} instead at line {1} column {2}.",
CurrentToken.Type, CurrentToken.Line, CurrentToken.Column));
}