Re: [Mathlib-develop] Path Function & problems with funcion calls

[Stefan M. <st...@he...>]

mark wrote:
> On Thursday 20 Feb 2003 7:40 pm, Stefan Mueller wrote:
> 
>>>While testing it I notived a problem with function calls
>>>
>>>entering
>>>
>>>
>>>>path
>>>
>>>runs the path function and sets the ans variable but doesn't display
>>>anything
>>>
>>>while entering
>>>
>>>
>>>>path()
>>>
>>>displays the result of the function call.
>>
>>I'll have a look into it.
>>
>>Kind regards,
>>   Stefan.
> 
> 
> 
> This seems to be connected to the function being treated as a variable rather 
> than a function when the brackets are ommitted.
> 
> There is a similar problem if there is a space between the function name and 
> the brackets. If you enter
> 
>>sin (5)
> 
> 
> then you get a null pointer error.
> 
> After checking it seems that MathLib treats VariableTokens and FunctionTokens 
> in the same way. It first checks for a variable with that name then for a 
> function.
> 
> Therefore it might be an idea to combine VariableTokens and FunctionTokens 
> into one class (Say ReferenceToken) since this would ensure consistent 
> behaviour regardless of how the function or variable is entered.
> 
> One difficulty is the fact that VariableToken descends from OperandToken while  
> FunctionToken descends from OperatorToken. RefereenceToken would have to be a 
> subclass of OperandToken which would mean that it would have to store any 
> parameters being passed to the variable or function.
> 
> Though this would have the advantage of making functions more consistent with 
> keyword functions such as IF and WHILE.

You're right, the mentioned approach looks very nice. There is also
another advantage. To move functions into a descendent of OperandToken
would clean up the handling of Expression-Tokens. In the future
expression-tokens should only handle operands like +,*/^   this will
simplify handling of priorities and evaluation of expressions.

I'll start working on it right away. I propose to call the new
token FunctionVariable-token since it cannot be determined during
parsing if a token is a variable or a function.

Kind regards,
   Stefan.