Re: [Chicken-users] Recursive define-macro

[Kon Lovett]

On Mar 7, 2007, at 12:37 AM, felix winkelmann wrote:

> On 3/7/07, Joshua Griffith <address@hidden> wrote:
> > I get an unbound variable error when I execute the following:
> > (define-macro (test alist) (if (> 0 (length alist)) (test (cdr  
> > alist))))

I think this explains the above error:

#;1> rec
Error: unbound variable: rec
#;1> (macro? 'rec)
#t

A variable bound to a macro is not a regular variable.

If you need to recurse to perform macro expansion just use any of the  
syntax forms that help - named let, rec, repeat, do, etc.

> > Are recursive define-macro definitions possible?
>
> The code inside a macro is executed at macro-expansion time,
> and should probably not refer to itself for expansion. A macro
> can be recursive by *expanding* into code that refers to the macro
> (but that might end in endless recursion).

Yeah, using the macro expansion machinery to perform recursive  
expansion can work but tricky. A technique that might called "clever".

> cheers,
> felix
>
>
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