SPUG: first vs //

[Colin Meyer]

On Wed, Jul 18, 2007 at 11:37:42AM -0700, Michael R. Wolf wrote:
> > Interestingly, Larry's 'first' suggestion is now available in the core:
> > 
> >    use List::Util qw/first/;
> > 
> >    $var  = first { defined } $foo, $bar, $baz;
> 
> In the world of TMTOWTDI, I like.... *both*.
> 
> I initially liked the use of 'first' as more intuitive (for my definition of
> intuitive).  In reading the "old arguments", I realized that the 'first'
> subroutine does not (in fact, cannot) do short circuiting, in which case the
> // operator is better.
> 
> $var = $foo // $bar // $baz;
> 
> Short circuiting (lazy evaluation) makes much more sense when functions are
> called since they could have a non-trivial cost and side-effects that may
> need to be avoided.  In some cases the later functions must be guarded
> against execution if earlier ones succeed.
> 
> $var = foo() // bar() // baz();

Short circuiting with first: 

    $var = first { $_->() } \( &foo, &bar, &baz );

-Colin.