Re: [Chicken-users] hygienic egg PORT-A-MANIA!

[Tobia Conforto]

Alan Post wrote:
> (define-macro (char->number ch)
>  `(- (char->integer ,ch)
>      (char->integer #\0)))
>
> (define-macro (0= n)
>  `(= 0 ,n))
>
> (define-macro (begin0 form . forms)
>  (let ((var (gensym)))
>    `(let ((,var ,form)) ,@forms ,var)))
>
> If |define-macro| is no longer around, how would the above forms be  
> written?

With Scheme's standard high-level, hygienic macros, that Chicken now  
supports natively:

(define-syntax char->number
  (syntax-rules ()
    ((char->number ch)
     (- (char->integer ch)
        (char->integer #\0)))))

(define-syntax 0=
  (syntax-rules ()
    ((0= n)
     (= 0 n))))

(define-syntax begin0
  (syntax-rules ()
    ((begin0 form forms ...)
     (let ((temp form))
       forms ...
       temp))))

This is kind of the whole point of the hygienic branch ;-)

Notice how more readable they are, without commas and stuff.  Yes, the  
"..." is very clever and does what you would expect and no, temp won't  
collide with *any* other variable named temp, whatsoever.  No more  
gensym and quasiquote!

On the other hand, why are these written as macros in the first place?


Tobia