On 2011-11-16, at 2:54 PM, Bradley Lucier wrote:

Marc:

Here's the contents of a file:

(declare (standard-bindings) (extended-bindings) (block))

(declare (not inline))

(define (safe-fixnum-+ x y) (declare (fixnum)) (+ x y))

Here's the expansion:

[Bradley-Luciers-MacBook-Pro:~/programs/gambc-v4_6_2-devel] lucier% gsc -c -expansion crap.scm Expansion:

(define safe-fixnum-+ (lambda (x y) (if (and ('#<procedure #2 ##fixnum?> y) ('#<procedure #2 ##fixnum?> x)) (let ((temp.2 ('#<procedure #3 ##fx+?> x y))) (if temp.2 temp.2 (if (and ('#<procedure #2 ##fixnum?> y) ('#<procedure #2 ##fixnum?> x)) (let ((temp.5 ('#<procedure #3 ##fx+?> x y))) (if temp.5 temp.5 ('#<procedure #4 fx+> x y))) ('#<procedure #4 fx+> x y)))) (if (and ('#<procedure #2 ##fixnum?> y) ('#<procedure #2 ##fixnum?> x)) (let ((temp.8 ('#<procedure #3 ##fx+?> x y))) (if temp.8 temp.8 ('#<procedure #4 fx+> x y))) ('#<procedure #4 fx+> x y)))))

The C code generated by gsc matches the expansion.

This is very strange results---checking three times whether x and y are fixnums? I can't understand this.

Yes very strange... On the other hand testing for fixnum 3 times has the advantage that it tolerates cosmic rays which could change some bits in the processor for the values x and y... Hey I could probably sell this idea to NASA or DoD! Seriously, I will investigate. Marc