private AST_operand Parse_operand(TokenKind followSet)
{
IncrementDepth();
DebugPrint("opnd");
Token t = LookAheadToken();
AST_operand operand;
switch (t.Kind)
{
case int_Literal:
operand = Parse_integer_literal();
break;
case string_Literal:
operand = Parse_string_literal();
break;
case bool_Literal:
operand = Parse_bool_literal(followSet);
break;
case Identifier:
operand = Parse_identifier(followSet);
break;
case OpenParenthesis:
Match(OpenParenthesis);
operand = new AST_expression_operand(Parse_expression(followSet | CloseParenthesis));
if (LookAheadToken().Kind == CloseParenthesis)
{
Match(CloseParenthesis);
}
else
{
Error("')' expected, '" + LookAheadToken().ToString() + "' found.", LookAheadToken());
SkipUntilFollow(followSet | CloseParenthesis);
if (LookAheadToken().Kind == CloseParenthesis)
{
Match(CloseParenthesis);
}
}
break;
default:
Error("Operand expected. '" + t.ToString() + "' does not start an operand.", t);
SkipUntilFollow(followSet);
operand = new ASTDummy_operand();
break;
}
operand.Row = t.Row;
operand.Column = t.Column;
DecrementDepth();
return(operand);
}
private AST_expression Parse_expression(TokenKind followSet)
{
IncrementDepth();
DebugPrint("expr");
AST_expression expression;
Token t = LookAheadToken();
switch (t.Kind)
{
case Exclamation:
expression = Parse_unary_operator_operand(followSet);
break;
default:
if (isMemberOf(t.Kind, FirstSet_operand))
{
AST_operand left_operand = Parse_operand(followSet | BinaryOperators);
if (IsBinaryOperator(LookAheadToken().Kind))
{
AST_binary_operator binary_operator = Parse_binary_operator(followSet);
AST_operand right_operand = Parse_operand(followSet);
binary_operator.SetLeft(left_operand);
binary_operator.SetRight(right_operand);
expression = binary_operator;
}
else
{
expression = left_operand;
}
}
else
{
Error("Expression expected. '" + t.ToString() + "' does not start an expression.", t);
expression = new ASTDummy_operand();
SkipUntilFollow(followSet);
}
break;
}
DecrementDepth();
return(expression);
}
public virtual void Visit(ASTDummy_operand dummy_operand)
{
}