[Chicken-users] Re: number->string bug

[Kevin Beranek]

One thing I forgot to mention is that any of the numbers that provide
the wrong output in the code below work correctly when evaluating them
in isolation, like at the csi prompt.


On Tue, Jan 06, 2009 at 09:20:32PM -0600, Kevin Beranek wrote:
> I've stumbled upon some interesting behavior of number->string.  It
> appears that there was previously a ticket filed for a similar bug in
> version 2.6 (http://trac.callcc.org/ticket/160).  What I've been
> observing doesn't seem to be exactly the same but it is perhaps related
> because I've only noticed it with base 2 as was the case with the
> previous bug.
> 
> Below is a test case followed by some sample output.  One interesting
> thing to note about the output is that (number->string 99 2) produced
> two different values (2 and 75).  Also of note is that I've tried
> various constructions of the following code with let statements at
> different levels, using let vs. set! in different places and different
> methods of looping but the bug remains in every combination I've tried.
> Behavior is also unchanged between csi and csc.
> 
> Just to be clear about what the code below is intended to do, it is
> randomly constructing values in a given range, converting them to a
> binary string via number->string, determining if the string is valid by
> checking that all characters in the string are either #\0 or #\1 and if
> not it prints the offending value along with the generated string.
> 
> CODE:
> 
> (let ((i 0) (val 0) (binary-val 0) (invalid #f) (j 0) (c 0))
> 
>   (do ((i 0 (+ i 1))) ((= i 5000))
>     (set! val (random 100))
>     (set! binary-val (number->string val 2))
>     (set! invalid #f) 
> 
>     (do ((j 0 (+ j 1))) ((= j (string-length binary-val)))
>       (set! c (string-ref binary-val j))
>       (if (not (or (char=? c #\0) (char=? c #\1)))
>         (set! invalid #t)))
>     
>     (if invalid
>       (printf "(number->string ~a 2) = ~a\n" val binary-val))))
> 
> OUTPUT:
> 
> (number->string 99 2) = 2
> (number->string 51 2) = 99
> (number->string 8 2) = 51
> (number->string 30 2) = 8
> (number->string 2 2) = 30
> (number->string 75 2) = 2
> (number->string 99 2) = 75
> 
> 
> -- 
> Kevin Beranek

-- 
Kevin Beranek