On Thu, Jul 18, 2002 at 11:39:15PM -0400, belg4mit wrote:
> Heh I just came across this today. It's an interesting optimization,
> but does it occur that often? It also precludes the possiblity of action at a
> distance / more complicated sort blocks/subroutines doing more than just
> sorting...
If sort is used in void or scalar context it's a no-op, that's about the
extent of the optimization. Very simplistic, nothing like Haskell.
In fact, perl will warn you about this, but the fellow below didn't have
warnings on.
$ perl -wle 'sort {print "a:$a\tb:$b"; $a cmp $b} qw(5 2 3 4 1)'
Useless use of sort in void context at -e line 1.
$ perl5.8.0 -wle '$a = sort {print "a:$a\tb:$b"; $a cmp $b} qw(5 2 3 4 1)'
Useless use of sort in scalar context at -e line 1.
The behavior of sort in scalar context is officially undefined because
nobody could agree on what it should do. This causes subtle bugs.
$ perl -wle 'sub foo { return sort qw(3 2 1) } print scalar foo'
Use of uninitialized value in print at -e line 1.
--
Michael G. Schwern <[EMAIL PROTECTED]> http://www.pobox.com/~schwern/
Perl Quality Assurance <[EMAIL PROTECTED]> Kwalitee Is Job One
Let me check my notes.
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