Re: [Chicken-users] fixnum-specific math operators patch

[Kon Lovett]

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On Sep 1, 2006, at 7:15 AM, Will M Farr wrote:

> Hello all,
>
> On Sep 1, 2006, at 3:06 AM, Kon Lovett wrote:
<snip>
> 3. My opinion is that The Right Thing (TM) is to code the macro as  
> follows:
>
> (define-syntax do-range
>   (syntax-rules ()
>     ((_ (i aa bb) expr ...)
>      (let ((a aa)
>            (b bb))
>        (cond-expand
>         ((not unsafe)
>          (if (or (not (fixnum? a))
>                  (not (fixnum? b)))
>              (error 'do-range "non-fixnum limits" a b))))
>        (do ((i a (fx+ i 1)))
>            ((fx= i b))
>          expr ...)))))
>
> This works, but it's pretty yucky.  It is the simplest way, given  
> the present behavior of the fxXXX operators, to achieve safety in  
> safe mode (with useful, and immediate, error reporting) and speed  
> in unsafe mode.  I submitted the fixnum patch because it would  
> implement the same behavior, but without requiring people using the  
> fxXXX operators to think so much about these issues (and type (cond- 
> expand ...) every time).
>
> Perhaps this situation is familiar to other Chicken users, but I  
> didn't realize that something like #3 was needed to be both safe  
> and fast until yesterday.  This is just food for thought---I  
> understand if felix and others want to keep the present behavior of  
> the fxXXX operators.

Good food. (Made me think to re-visit some older code that had some  
ASSumptions about the public interface arguments.)

But Felix's point about 'ensure' should help w/ syntax forms that  
have domain & range restrictions.

Best wishes,
Kon

> Will

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