Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!ames!elroy!gryphon!joe
From: joe@gryphon.COM (Joseph Francis)
Newsgroups: comp.lang.c
Subject: Re: printf() and commutative operations problem
Keywords: C printf
Message-ID: <15580@gryphon.COM>
Date: 8 May 89 07:27:07 GMT
References: <etc...>
Reply-To: joe@gryphon.COM (Joseph Francis)
Organization: Trailing Edge Technology, Redondo Beach, CA
Lines: 19

The problem having been well characterized, why not a new specification
for evaluation. The bitwise & operator is well-known to be commutative
so it is left to the compiler to rearrange subterms for optimal
evaluation, and therefore the 'deadly' getchar() used as 
getchar() & getchar() (useless, but similar to the original problem) combined
with something else can have unpredictable side-effects.  However, the
getchar() && getchar() will always be L-R evaluated.  So, for function
definition, why not something like f(a, b; c; d, e, f) either in the
prototype or at invocation which guarantees the ordering of b->c->d
and leaves the others unspecified; mixed commtative and non-commutative
argument delimiting.  I realize, of course, this could be controlled with
macros, something hideous like 
#def f(A,B,C) { argtype a,b,c; a=A; b=B; c=C; g(a,b,c) }
or with better coding, but why not allow more sequencing control, if you
allow it with && and other operators?

-- 
joe@gryphon		...!elroy!gryphon!joe	
but jojo to my beeeest frieeeends.