On 08/06/11 13:41, Paul Makepeace wrote:
On Wed, Jun 8, 2011 at 13:17, Tom Hukins<t...@eborcom.com> wrote:
On Wed, Jun 08, 2011 at 02:00:41PM +0200, Abigail wrote:
I'd rather go for sacking people that don't know the difference
between
if (something) { ... }
and
unless (!something) { ... }
It's sunny outside and pubs are open: I can think of worse times to
lose my job.
Or does everyone think they are always equivalent?
I'm not everyone, and with a language as flexible as Perl I hesitate
to make strong statements involving words like "always", but I don't
recall encountering a situation where they differ.
$ perl -le 'print "$_ == !!$_ ? ", $_ == !!$_ ? "yes" : "no" for (-1,
0, 1, 2, undef)'
-1 == !!-1 ? no
0 == !!0 ? yes
1 == !!1 ? yes
2 == !!2 ? no
== !! ? yes
But:
$ perl -le 'print 0 eq !!0 ? "yes" : "no"'
no
This still wouldn't affect the behaviour of the original example. In the
context of an if or unless statement, the only thing that matters is the
boolean value of the expression, not exactly which true or false value
it is. Perl's canonical true and false are 1 and '' respectively, but
everything has a boolean value.
Matt
