Thanks Joe
I'll have a look at your approaches: I'll probably come back to you!
Best wishes
Hugh
On 31/1/05 3:23 pm, Joseph J. Strout at joe at realsoftware dot com wrote:
> At 2:58 PM +0000 1/31/05, Hugh Neill wrote:
>
>> I am an absolute beginner, except that I have worked the tutorial and
>> attempted to read various books.
>>
>> I am trying to design a program part of which will evaluate a function
>> supplied by the user.
>
> Wow, you're jumping right into the deep end. This is a very hard
> problem for a beginner. Val() does not do this for you, you have to
> work at it. Let me sketch out some approaches:
>
> 1. You can use an RBScript object. You'd need to feed it some source
> code that assigns the initial value of x, and then Prints the result
> of the expression the user entered. You'd get the answer in the
> Print event of the RBScript, which you could then display as you like.
>
> 2. You could write your own expression evaluator, probably using a
> simple recursive-descent parser. If this sounds like Greek to you,
> then you probably shouldn't attempt it until you get more experience
> under your belt. However, if you want to give it a try, I can send
> some sample code.
>
> 3. I believe that Bob Delaney has a plug-in that will evaluate
> expressions. Search the NUG archives. Bob has many math-related
> plugins, all very high quality and free.
>
> Best,
> - Joe
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