Which is the best implementation(in terms of speed and memory usage) for iterating through a Perl array? Is there any better way? (@Array
need not be retained).
foreach (@Array)
{
SubRoutine($_);
}
while($Element=shift(@Array))
{
SubRoutine($Element);
}
while(scalar(@Array) !=0)
{
$Element=shift(@Array);
SubRoutine($Element);
}
for my $i (0 .. $#Array)
{
SubRoutine($Array[$i]);
}
map { SubRoutine($_) } @Array ;
In terms of speed: #1 and #4, but not by much in most instances.
You could write a benchmark to confirm, but I suspect you'll find #1 and #4 to be slightly faster because the iteration work is done in C instead of Perl, and no needless copying of the array elements occurs. ($_
is aliased to the element in #1, but #2 and #3 actually copy the scalars from the array.)
#5 might be similar.
In terms memory usage: They're all the same except for #5.
for (@a)
is special-cased to avoid flattening the array. The loop iterates over the indexes of the array.
In terms of readability: #1.
In terms of flexibility: #1/#4 and #5.
#2 does not support elements that are false. #2 and #3 are destructive.