public static IExpression BuildExpression(TokenList tokens, Stack<int?> precedenceStack)
{
if (tokens.Current == null)
throw new TokenParserException("The script seems to have ended prematurely. Shouldn't there be something here?", tokens.Peek(-2));
Token token = tokens.Current;
IExpression expr = null;
bool endGroupedExpression = false;
switch (token.TokenType)
{
case TokenType.Number:
expr = new NumericExpression(tokens, precedenceStack);
break;
case TokenType.QuotedString:
expr = new StringExpression(tokens, precedenceStack);
break;
case TokenType.FreeText:
expr = new StringExpression(tokens, precedenceStack);
return expr;
case TokenType.Word:
if (expressionCreators.ContainsKey(token.Value))
{
// find the appropriate handler for this keyword
expr = expressionCreators[token.Value].Create();
}
else // we don't recognise the word, so we can assume it's a variable and validate it at run-time
{
// don't allow instruction keywords to be used as variable names
if (instructionCreators.ContainsKey(token.Value))
throw new TokenParserException("This word is the name of an instruction. You can't use it here in this context.", token);
else
expr = new VariableExpression();
}
// if applicable, have the expression prepare itself according to its own rules
if (expr is IFlexibleSyntaxExpression)
((IFlexibleSyntaxExpression)expr).PrepareExpression(tokens, precedenceStack);
else // otherwise just advance to the next token
tokens.Advance();
// chain together any properties and argument lists
expr = BuildDeepExpression(expr, tokens);
break;
case TokenType.PropertyDesignator:
// property designators are handled elsewhere. if we found one here, it's a parsing error.
if (tokens.Previous.TokenType == TokenType.Word)
throw new TokenParserException("This type of expression doesn't allow you to specify a property.", tokens.Next);
throw new TokenParserException("You've got a property designator in a spot where it doesn't belong.", tokens.Next);
case TokenType.GroupStart:
expr = BuildGroupedExpression(tokens);
break;
case TokenType.GroupEnd:
endGroupedExpression = true;
break;
default:
throw new TokenParserException("This part of the script should equate to a value but instead I got \"" + token.Value + "\", which doesn't really mean anything in this context.", token);
}
if (!endGroupedExpression)
{
int? precedence = precedenceStack.Peek();
while (NextHasGreaterPrecedence(precedence, tokens))
expr = BuildBinaryExpression(tokens, expr, precedenceStack);
}
return expr;
}
public static IExpression BuildExpression(TokenList tokens, Stack <int?> precedenceStack)
{
if (tokens.Current == null)
{
throw new TokenParserException("The script seems to have ended prematurely. Shouldn't there be something here?", tokens.Peek(-2));
}
Token token = tokens.Current;
IExpression expr = null;
bool endGroupedExpression = false;
switch (token.TokenType)
{
case TokenType.Number:
expr = new NumericExpression(tokens, precedenceStack);
break;
case TokenType.QuotedString:
expr = new StringExpression(tokens, precedenceStack);
break;
case TokenType.FreeText:
expr = new StringExpression(tokens, precedenceStack);
return(expr);
case TokenType.Word:
if (expressionCreators.ContainsKey(token.Value))
{
// find the appropriate handler for this keyword
expr = expressionCreators[token.Value].Create();
}
else // we don't recognise the word, so we can assume it's a variable and validate it at run-time
{
// don't allow instruction keywords to be used as variable names
if (instructionCreators.ContainsKey(token.Value))
{
throw new TokenParserException("This word is the name of an instruction. You can't use it here in this context.", token);
}
else
{
expr = new VariableExpression();
}
}
// if applicable, have the expression prepare itself according to its own rules
if (expr is IFlexibleSyntaxExpression)
{
((IFlexibleSyntaxExpression)expr).PrepareExpression(tokens, precedenceStack);
}
else // otherwise just advance to the next token
{
tokens.Advance();
}
// chain together any properties and argument lists
expr = BuildDeepExpression(expr, tokens);
break;
case TokenType.PropertyDesignator:
// property designators are handled elsewhere. if we found one here, it's a parsing error.
if (tokens.Previous.TokenType == TokenType.Word)
{
throw new TokenParserException("This type of expression doesn't allow you to specify a property.", tokens.Next);
}
throw new TokenParserException("You've got a property designator in a spot where it doesn't belong.", tokens.Next);
case TokenType.GroupStart:
expr = BuildGroupedExpression(tokens);
break;
case TokenType.GroupEnd:
endGroupedExpression = true;
break;
default:
throw new TokenParserException("This part of the script should equate to a value but instead I got \"" + token.Value + "\", which doesn't really mean anything in this context.", token);
}
if (!endGroupedExpression)
{
int?precedence = precedenceStack.Peek();
while (NextHasGreaterPrecedence(precedence, tokens))
{
expr = BuildBinaryExpression(tokens, expr, precedenceStack);
}
}
return(expr);
}