Re: string parsing/preparation for latex

[Jon Wilson]

Hi Stephen,
Yeah, I guess you're right.  Like I said, I'm new to the whole idea of
macros, and I'm kind of looking for a really good use-case for the
things.  Can you suggest a non-contrived situation in which a macro
would be the best solution?
Regards,
Jon

Stephen Compall wrote:
> On Wed, 2005-11-09 at 07:24 -0600, Jon Wilson wrote:
>
> > scheme->LaTeX would have to be a macro, then it receives its arguments
> > before they are evaluated.  Unless of course I'm mistaken about the
> > nature of macros.  (I'm still relatively new to the idea.)
>
>
> Yes, but you'd lose more than you'd gain by making it a macro.  Unless
> you really wanted to do something crazy like:
>
> (define-syntax scheme->LaTeX
>   (syntax-rules (+ /)
>     ((_ (+ f1 f2 ... f3))
>      (string-append "(" (scheme->LaTeX (+ f1 f2 ...))
>                     " + " (scheme->LaTeX f3) ")"))
>     ((_ (+ f1))
>      (scheme->LaTeX f1))
>     ((_ (/ f1 f2 f3 ...))
>      (string-append "\frac{" (scheme->LaTeX f1)
>                     "}{" (scheme->LaTeX (* f2 f3 ...)) "}"))
>     ;;and so on....
>     ))
>
> Of course that has many drawbacks of its own.  Better to just handle it
> in functions, which, for example, wouldn't have the spurious parenthesis
> problem of the multiple + argument syntax, and so on.  Not to mention
> the added benefit of scheme->LaTeXing forms unknown at load-time without
> using eval.
>
> Remember Norvig's first step to writing a macro: Decide if the macro is
> really necessary.