public virtual object Visit(NullAstNode node)
{
return(null);
}
/// <summary>
/// factor : PLUS factor
/// | MINUS factor
/// | INTEGER_CONST
/// | REAL_CONST
/// | STRING_CONST
/// | LPAREN statement RPAREN
/// | NOT factor
/// | variable_access
/// | null
/// | true
/// | false
/// </summary>
private AstNode ParseFactor()
{
AstNode node = null;
EatWhiteSpace();
var token = CurrentToken;
switch (token.Type)
{
case TokenType.PLUS:
Eat(TokenType.PLUS);
node = new UnaryOperationAstNode(token, ParseFactor());
break;
case TokenType.MINUS:
Eat(TokenType.MINUS);
node = new UnaryOperationAstNode(token, ParseFactor());
break;
case TokenType.INTEGER_CONST:
Eat(TokenType.INTEGER_CONST);
node = new TerminalAstNode <int>(token, int.Parse(token.Value));
break;
case TokenType.REAL_CONST:
Eat(TokenType.REAL_CONST);
node = new TerminalAstNode <double>(token, double.Parse(token.Value));
break;
case TokenType.TEXT_LITERAL:
Eat(TokenType.TEXT_LITERAL);
node = new TerminalAstNode <string>(token, token.Value);
break;
case TokenType.IDENTIFIER:
node = ParseVariableAccess();
break;
case TokenType.NULL:
Eat(TokenType.NULL);
node = new NullAstNode(token);
break;
case TokenType.BOOL_FALSE:
Eat(TokenType.BOOL_FALSE);
node = new TerminalAstNode <bool>(token, false);
break;
case TokenType.BOOL_TRUE:
Eat(TokenType.BOOL_TRUE);
node = new TerminalAstNode <bool>(token, true);
break;
case TokenType.LPAREN:
Eat(TokenType.LPAREN);
node = ParseStatement();
Eat(TokenType.RPAREN);
break;
case TokenType.NOT:
Eat(TokenType.NOT);
node = ParseFactor();
break;
}
return(node);
}
public override object Visit(NullAstNode node)
{
return(null);
}
