bool IfTagOption::TryParseExpression(ParserContext& context)
{
Token* token,
* lhsToken = NULL,
* rhsToken = NULL,
* unaryToken = NULL;
ConditionalOperator conditionalOperator;
UnaryOperator unaryOperator = UnaryAnd;
// Evaluate the expressions
do
{
// Get the LHS token
if (!context.TryNext(token))
{
context.Error.Description = "unexpected end of file while parsing condition";
return false;
}
// Ensure the type of the LHS
if (!IsValidFragment(token))
return context.Error.Set(token,
"invalid left hand side of expression: " + token->Value);
// Save the LHS token
lhsToken = token;
// Get the operator token
if (!context.TryNext(token))
return context.Error.Set(token,
"unexpected end of file while parsing condition");
// Check the type
if (token->Type & TokenOperator)
{
// Check the operator
if (token->Value == "==")
conditionalOperator = ConditionalEquals;
else if ((token->Value == "!=") ||
(token->Value == "<>"))
conditionalOperator = ConditionalNotEquals;
else if (token->Value == ">")
conditionalOperator = ConditionalGreaterThan;
else if (token->Value == "<")
conditionalOperator = ConditionalLessThan;
else if (token->Value == ">=")
conditionalOperator = ConditionalGreaterThanOrEquals;
else if (token->Value == "<=")
conditionalOperator = ConditionalLessThanOrEquals;
else
return context.Error.Set(token,
"invalid expression operator: " + token->Value);
// Get the RHS token
if (!context.TryNext(token))
return context.Error.Set(token,
"unexpected end of file while parsing condition");
// Check the type
if (!IsValidFragment(token))
return context.Error.Set(token,
"invalid right hand side of expression: " + token->Value);
// Store the RHS token
rhsToken = token;
// Try to get the unary operator
if (!context.TryNext(token))
return context.Error.Set(token,
"unexpected end of file while parsing condition");
}
else
conditionalOperator = ConditionalImplicit;
// Evaluate the unary operator
if (token->Type & TokenIdentifier)
{
// Ensure that this is a unary operator
if (token->Value == "and")
unaryOperator = UnaryAnd;
else if (token->Value == "or")
unaryOperator = UnaryOr;
else
return context.Error.Set(token,
"invalid unary operator: " + token->Value);
// Store the unary operator token
unaryToken = token;
}
else
unaryToken = NULL;
// Construct the condition
Condition* condition = new Condition(lhsToken,
conditionalOperator,
rhsToken);
if (this->_rootCondition)
condition->Attach(this->_rootCondition,
unaryOperator);
this->_rootCondition = condition;
// Reset the stored tokens
lhsToken = NULL;
rhsToken = NULL;
}
while (unaryToken != NULL);
// Ensure that this is a closing tag
if (!(token->Type & TokenTagClose))
return context.Error.Set(token,
"expected end of tag but got " + token->Value);
// Done
return true;
}
