public object Evaluate()
{
if (expression == null)
{
throw new ExpressionEvaluatorException("the expression should not be empty or null");
}
object result;
try
{
ExpressionLexer lexer = new ExpressionLexer(expression);
ExpressionParser parser = new ExpressionParser(
new TokenStream(lexer),
context);
ExpressionNode tree = parser.Parse();
ExpressionVisitor visitor = new ExpressionVisitor(context);
IExpression expr = ExpressionBuilder.Build(tree);
expr.Accept(visitor);
result = visitor.EvaluationResult;
}
catch (Exception e) // reports all unexpected exceptions
{
context.ReportError(
String.Format(
"failed to evaluate expression '{0}' : '{1}'",
expression,
e.Message));
result = expression;
}
return(result);
}
/// <summary>
/// The Literal operation
/// </summary>
/// <returns>An expression node created based on the operation</returns>
protected ExpressionNode Literal()
{
if (currentToken.Text.Length > 0)
{
if (currentToken.Type == TokenType.Integer)
{
int res;
if (TryConvertNumber(currentToken.Text, out res))
{
ExpressionNode integer = new ExpressionNode(
new Token(TokenType.Integer, res.ToString()));
GetNextToken();
return(integer);
}
else
{
throw new ExpressionEvaluatorException(
String.Format("invalid number '{0}'", currentToken.Text));
}
}
else if (currentToken.Type == TokenType.String)
{
int x;
if (!context.TryResolveSymbol(currentToken.Text, out x))
{
string tokenText = currentToken.Text;
while (true)
{
if (context.Variables != null &&
!context.Variables.ContainsKey(currentToken.Text) &&
!DatatypeInfoProvider.IsPredefinedDatatype(currentToken.Text) &&
!DatatypeInfoProvider.isPredefinedModifier(currentToken.Text))
{
string typeInfo;
if (context.TryResolveCustomType(currentToken.Text, out typeInfo))
{
tokenText = typeInfo;
break;
}
else
{
context.ReportError(
String.Format("cannot resolve symbol '{0}'", currentToken.Text));
break;
}
}
if (context.Variables != null &&
context.Variables.ContainsKey(currentToken.Text))
{
tokenText = currentToken.Text;
break;
}
// treat predefinedModifier as empty node
if (DatatypeInfoProvider.isPredefinedModifier(currentToken.Text))
{
GetNextToken();
}
else if (DatatypeInfoProvider.IsPredefinedDatatype(currentToken.Text))
{
tokenText = currentToken.Text;
break;
}
}
// in order to get pointer type size and avoid related issue
bool isPointerType = false;
GetNextToken();
if (isInSizeOf)
{
while (currentToken.Text == "*")
{
GetNextToken();
isPointerType = true;
}
}
if (isPointerType)
{
ExpressionNode integer = new ExpressionNode(
new Token(TokenType.Integer, "4"));
return(integer);
}
ExpressionNode variable = new ExpressionNode(
new Token(TokenType.Variable, tokenText));
return(variable);
}
else if (isInSizeOf)
{
string tokenText = currentToken.Text;
GetNextToken();
//ignoring other expression
while (currentToken.Text != ")")
{
GetNextToken();
}
return(new ExpressionNode(
new Token(TokenType.Variable, tokenText)));
}
else
{
GetNextToken();
return(new ExpressionNode(
new Token(TokenType.Integer, x.ToString())));
}
}
else
{
throw new ExpressionEvaluatorException(
String.Format("unexpected token '{0}'", currentToken));
}
}
else
{
throw new ExpressionEvaluatorException("unexpected end of input");
}
}
