Macro expansion

Macro expansion

[Hans Aberg]

In the code below the 'loop' and 'begin' examples will execute the  
'while' loop, but if put into the body of a function, 'while' will not  
run. So why, and how to fix it?

Just copy and paste the examples below into guile. For the two first,  
I get
   0123456789
   0123456789done!3
but for the third, the thunk, only
   done!3
So the macro 'while' is not expanded as expected.

   Hans


(use-syntax (ice-9 syncase))

(define-syntax loop
   (syntax-rules ()
     ((loop (j ...) p (r ...) (x ...))
       (begin j ... (while p x ... r ...)))
))

(loop ((define i 0))
      (< i 10)
      ((set! i (+ i 1)))
      ((display i)))

(begin
   (loop ((define i 0))
        (< i 10)
        ((set! i (+ i 1)))
        ((display i)))
   (display "done!")
   (+ 1 2)
)

((lambda
   ()
   (begin
     (loop ((define i 0))
          (< i 10)
          ((set! i (+ i 1)))
          ((display i)))
     (display "done!")
     (+ 1 2)
   )
))

Re: Macro expansion

[Neil Jerram]

Hans Aberg <haberg-1@telia.com> writes:

> In the code below the 'loop' and 'begin' examples will execute the
> while' loop, but if put into the body of a function, 'while' will not
> run. So why, and how to fix it?
>
> Just copy and paste the examples below into guile. For the two first,
> I get
>   0123456789
>   0123456789done!3
> but for the third, the thunk, only
>   done!3

With my current Guile,

scheme@(guile-user)> (version)
$4 = "1.9.14.17-44f43"

the third case behaves as you would expect:

scheme@(guile-user)> ((lambda
  ()
  (begin
    (loop ((define i 0))
         (< i 10)
         ((set! i (+ i 1)))
         ((display i)))
    (display "done!")
    (+ 1 2)
  )
))
0123456789done!$5 = 3

Regards,
        Neil

Re: Macro expansion

[Hans Aberg]

On 15 Jan 2011, at 21:39, Neil Jerram wrote:

> With my current Guile,
>
> scheme@(guile-user)> (version)
> $4 = "1.9.14.17-44f43"
>
> the third case behaves as you would expect:

That is right, I used the stable versions 1.8.x, x = 7, 8.  
Unfortunately, when I try to install guile-1.9.14, I get the error  
below (Mac OS X 10.5.8 PPC G4).



ld: duplicate symbol ___gmpz_abs in .libs/libguile_2.0_la-arbiters.o  
and .libs/libguile_2.0_la-alist.o

Re: Macro expansion

[Hans Aberg]

On 15 Jan 2011, at 21:39, Neil Jerram wrote:

> With my current Guile,
>
> scheme@(guile-user)> (version)
> $4 = "1.9.14.17-44f43"
>
> the third case behaves as you would expect:

When I upgrade, then it too works. So it was a bug that has been  
fixed, then.

scheme@(guile-user)> (version)
$1 = "1.9.14.68-a7d8a"