p5pRT
commented
19 years ago From perl-bug@owl.me.uk
Created by perl-bug@owl.me.uk
Dear all\,
I have noticed that including an array deref in the return statement of a sub causes unusual results when that sub is called in scalar context.
Take the following script as an example:
--- start --- #!/usr/bin/perl
use strict; use warnings; use English; local $OFS = ' '; local $ORS = "\n";
sub a { my $foo = ['dick'\, 'harry']; my @bar = ('tom'\, @$foo); return @bar; }
sub b { my $foo = ['tom'\, 'dick'\, 'harry']; return @$foo; }
sub c { my $foo = ['dick'\, 'harry']; return ('tom'\, @$foo); }
sub d { my $foo = ['tom'\, 'dick']; return (@$foo\, 'harry'); }
print a; print b; print c; print d;
print scalar a; print scalar b; print scalar c; print scalar d; --- end ---
The output is as follows:
--- start --- tom dick harry tom dick harry tom dick harry tom dick harry 3 3 2 harry --- end ---
All four subs return the list ('tom'\, 'dick'\, 'harry') when called in array context. However\, only the first two return the value 3 (what I would expect\, the size of this array) when called in array context.
sub c\, which returns a list containing a scalar and a deref'd array ref\, returns 2 instead of 3. I guessed this might be the compiler noticing that two things are returned by c and optimising the return into something like "return wantarray ? ('tom'\, @$foo) : 2"\, although I doubt this is the behaviour most users would expect\, since the list returned in array context certainly has 3 elements. If this is the intended behaviour\, I would think that the warnings pragma should generate a warning in this case.
sub d is even more interesting\, since that evaluates to 'harry' in scalar context. I don't know if this is intended\, but again it seems counter-intuitive to me\, and it would\, too\, probably benefit from a warning.
Thanks for listening!
~ Rich
Migrated from rt.perl.org#34582 (status was 'resolved')
Searchable as RT34582$