Re: [Slib-discuss] Minor printf bug?

[Aubrey Jaffer]

 | From: Kris De Volder <address@hidden>
 | Date: Sun, 07 Dec 2008 12:10:24 -0800
 | 
 | I ran across a problem with the SLIB printf library, which I
 | *suspect* may be a minor bug.  I say *suspect* because it is of
 | course also possibly a bug in my code or my understanding of how
 | things ought to work, instead of a bug in slib code.  Either way
 | I'd like to do something about the bug...  whatever kind of bug it
 | may be :-)

See patch below.

 | The Slib FAQ doesn't talk about reporting bugs.  So I gather the
 | list may be a good place.  I apologize if it is not.  If so, please
 | point me to a good way/place to report bugs in the future.

slib-discuss is good.

 | Now for the "bug report".
 | 
 | Steps to reproduce:
 | 
 |   1) you will need a Scheme implementation which does not support the 
 |        multiarg-apply feature.
 | 
 |    E.g. you could outcomment ;multiarg apply line in XXX-init file and
 |    then
 | 
 |    (define apply 
 |       (let ((old-apply apply))
 |          (lambda (p a) (old-apply p a))))
 | 
 |   2) In a Scheme repl evaluate following
 | 
 | > (require 'printf)
 | slib:load: 
"file:/home/kdvolder/workspaces/kscheme/ca.kscheme/bin/slib/printf"
 | slib:load: 
"file:/home/kdvolder/workspaces/kscheme/ca.kscheme/bin/slib/strcase"
 | slib:load: 
"file:/home/kdvolder/workspaces/kscheme/ca.kscheme/bin/slib/sc4opt"
 | > (printf "Hello World")
 | 
 | The following error is reported (by my Scheme implementation, which is
 | not yet publically available)
 | 
 | > (printf "Hello world")
 | ...
 | It appears that the printf module is using multiarg apply, which is not
 | provided (yet) by my implementation.
 | 
 | When I check slib:features
 | > slib:features
 | -> (rev4-optional-procedures string-case printf dynamic-wind source
 | vicinity srfi-59 srfi-96 r4rs ieee-p1178 full-continuation defmacro)
 | 
 | Is this a bug?  I reasoned that it is, because the printf library
 | should either
 |   - somehow explicitly or implicitly require the 'multiarg-apply
 |     feature
 |   - or not use multi-arg apply
 | 
 | From the slib:features list, it appears this environment does not
 | purport to support multiarg-apply...
 | 
 | Or maybe I am missing something and support of multiarg apply is
 | implied by one of the features that is in the list above, and my
 | implementation is in error because it did not actually provide
 | multiarg apply while (implicitly) claiming that it does?

"printf.scm" should explicitly require multiarg-apply.  Although
REQUIREs are transitive in many implementations, code should not
depend on that.

Thanks for finding that.  This patch fixes it (also committed to CVS).

*** printf.scm  20 Dec 2006 11:38:53 -0500      1.35
--- printf.scm  07 Dec 2008 16:00:10 -0500      
***************
*** 18,23 ****
--- 18,24 ----
  ;each case.
  
  (require 'string-case)
+ (require 'multiarg-apply)
  (require-if 'compiling 'generic-write)
  
  ;; Determine the case of digits > 9.  We assume this to be constant.

 | Anyway, I plan to resolve this issue by implementing
 | multiarg-apply, but I would still like to report this problem (if
 | it is indeed a bug) or clarify my misunderstanding (if it is not).

You needn't implement it.  (REQUIRE 'MULTIARG-APPLY) will load
slib/mulapply.scm, which redefines APPLY to take multiple arguments.