Keep It Simple, Stupid PerlMonks

### 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??

Thanks a lot. That helps.
• Comment on Re^2: Variable number of foreach loops (non-recursive solution)

Replies are listed 'Best First'.
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

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

Create A New User
Node Status?
node history
Node Type: note [id://1064930]
help
Chatterbox?

How do I use this? | Other CB clients
Other Users?
Others chanting in the Monastery: (6)
As of 2017-06-23 19:46 GMT
Sections?
Information?
Find Nodes?
Leftovers?
Voting Booth?
How many monitors do you use while coding?

Results (554 votes). Check out past polls.