Re: Value of a statement with modifier

from perlsub: "The return value of a subroutine is the value of the last expression evaluated."

this is a nice and subtle example (i had to run it too).. $_[0] is the last expression evaluated when the unless fails, so the sub just ends up returning the first argument..

good example for always using explict returns ...

  return $_[0] ? undef : 'hello';
# or:
  return 'hello' unless $_[0];
  return;
[download]

Comment on Re: Value of a statement with modifier Select or Download Code

Replies are listed 'Best First'.
Re^2: Value of a statement with modifier by LTjake (Prior) on Jan 22, 2007 at 18:18 UTC
A small quibble, but I believe the first example should be written as: `return $_[ 0 ] ? () : 'hello';` [download] -- "Go up to the next female stranger you see and tell her that her "body is a wonderland." My hypothesis is that she’ll be too busy laughing at you to even bother slapping you." (src)	[reply] [d/l]
Re^3: Value of a statement with modifier by hossman (Prior) on Jan 23, 2007 at 02:40 UTC
There is no one right answer... if you return an empty list to mean "false", the false-ish-ness could be lost (or other problems could arise) if your return value is "slurped" into another list context ... There's no substite for extensively documenting that your method may not work the way people think and making it their responsibility to force the calling context.	[reply]
Re^4: Value of a statement with modifier by diotalevi (Canon) on Jan 23, 2007 at 07:21 UTC
Returning undef for false is more broken than returning empty lists for false. At least an empty list is easily promoted to a false or undef value but an undef value in a list is not as easily demoted to a false value. I think all the people returning undef for false are shortsighted and I hope they never get their hands on my code. `sub empty {} if ( empty() ) { ... } # ok @foo = empty(); if ( @foo ) { ... } # ok sub returns_undef { undef } if ( returns_undef() ) { ... } # ok @foo = returns_undef(); if ( @foo ) { ... } # NOT OK if ( grep { defined } @foo ) { ... } # oh ok, now it's "better".` [download] ⠤⠤ ⠙⠊⠕⠞⠁⠇⠑⠧⠊	[reply] [d/l]


Perl Monk, Perl Meditation
	PerlMonks