On Wed, Mar 26, 2008 at 9:47 PM, Rob Dixon <[EMAIL PROTECTED]> wrote:
> Jay Savage wrote:
> >
> > If you want to see grep really shine, though, think about ways you
> > might use it to avoid calling print for every element in the return
> > list, e.g.
> >
> > print join "\n", grep {$_ % 2 == 0} @list;
>
> I think that's very misleading. Why should I want to avoid calling print
> for each element? What you've written is the sort of thing for which
> Perl gets a bad name - it's less readable and has no obvious benefits
> over
>
> print "$_\n" foreach grep { $_ % 2 == 0 } @list;
>
cmpthese(1000, {
'foreach' => sub { print "$_\n" for grep {$_ % 2 == 0} 0..1000; },
'join' => sub { print join "\n", grep {$_ % 2 == 0} 0..1000; },
});
Rate foreach join
foreach 40.7/s -- -20%
join 50.8/s 25% --
25% performance gain strikes me as a pretty obvious benefit. YMMV, of
course, depending on your data and memory performance, but in general,
function calls are expensive, and and print moreso than most, because
it requires a system call out to the OS. Calling a function like print
on each iteration through a loop is rarely the most efficient way to
do business.
This doesn't really have anything to do with Perl; it's true in any language.
Of course, efficiency, like beauty, is in the eye of the beholder. And
that's why I was clear with OP, that he should do whatever made the
most sense for him in his particular situation.
TIMTOWTDI isn't what gives Perl a bad name; it's what makes it the
wonderful, flexible tool that it is, and crates passionate groups of
users like this one.
> (It also doesn't print a terminating "\n")
>
I think you'll agree there are several trivial fixes for this. 'print
"\n"' jumps immediately to mind.
Best,
-- jay
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