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Re^2: Variable number of foreach loops (non-recursive solution)

by abhay180 (Acolyte)
on Nov 29, 2013 at 09:48 UTC ( #1064930=note: print w/ replies, xml ) Need Help??

Comment on Re^2: Variable number of foreach loops (non-recursive solution)
Re^3: Variable number of foreach loops (performance)
by BrowserUk (Pope) on Nov 29, 2013 at 11:23 UTC

    Just in case performance is a consideration:

    #! perl -slw use strict; use Algorithm::Loops qw[ NestedLoops ]; use Time::HiRes qw[ time ]; sub nFor(&@) { my $code = shift; my @indices = map { 0 } @_; # First set of indices is all zeroes my @sizes = map { scalar @$_ } @_; # Cache array sizes (optional) my $k; do { # Determine the array elements corresponding to the current se +t # of indices, and pass them to the closure: $code->( map { $_[$_][$indices[$_]] } 0..$#_ ); # Determine the next set of indices: for ($k = $#_; $k >= 0; $k--) { $indices[$k]++; if ($indices[$k] < $sizes[$k]) { last; } else { $indices[$k] = 0; } } # If $k went out-of-bounds, it means we're finished: } while ($k >= 0); } sub nForX(&@) { my $code = shift; my $n = shift; return $code->( @_ ) unless $n; for my $i ( @{ shift() } ) { &nForX( $code, $n-1, @_, $i ); } } my %stuff = ( A => [ 1..1000 ], B => [ 'a'..'z', 'A'..'Z' ], C => [ map chr, 33..47, 58..64, 92..96 ], ); my $start; for my $pat ( qw[ A::B A::C B::C A::B::C ] ) { print "\nProcessing $pat"; my @keys = split '::', $pat; $start = time; nForX { my @set = @_; } scalar @keys, @stuff{ @keys }; printf "\tRecursive: %f seconds\n", time - $start; $start = time; nFor { my @set = @_; } @stuff{ @keys }; printf "\tIterative: %f seconds\n", time - $start; $start = time; NestedLoops [ @stuff{ @keys } ], sub { my @set = @_; }; printf "\tNestedLoops %f seconds\n", time - $start; } __END__ C:\test>nforx Processing A::B Recursive: 0.107126 seconds Iterative: 0.227112 seconds NestedLoops 0.474461 seconds Processing A::C Recursive: 0.049802 seconds Iterative: 0.117263 seconds NestedLoops 0.235748 seconds Processing B::C Recursive: 0.002990 seconds Iterative: 0.006834 seconds NestedLoops 0.014829 seconds Processing A::B::C Recursive: 3.072954 seconds Iterative: 7.725672 seconds NestedLoops 15.938471 seconds

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