I much prefer the far simpler syntax of nFor.

And nothing's stopping you from providing that interface.

#! perl -slw
use strict;

use Algorithm::Loops qw( NestedLoops );

sub nFor(&@) {
    my $cb = shift;
    NestedLoops([ map [ 0..$_-1 ], @_ ], $cb);
}

my @digits = 1 .. 3;

nFor {
    print join '', @digits[ @_ ];
} ( 3 ) x 4;
[download]

than the tortuous documentation for NestedLoops which I've still never wrapped by brain around.

Say you want

apple, dog, 1
apple, dog, 2
apple, dog, III
apple, cat, 1
apple, cat, 2
apple, cat, III
apple, platypus, 1
apple, platypus, 2
apple, platypus, III
orange, dog, 1
orange, dog, 2
orange, dog, III
orange, cat, 1
orange, cat, 2
orange, cat, III
orange, platypus, 1
orange, platypus, 2
orange, platypus, III
tomato, dog, 1
tomato, dog, 2
tomato, dog, III
tomato, cat, 1
tomato, cat, 2
tomato, cat, III
tomato, platypus, 1
tomato, platypus, 2
tomato, platypus, III
[download]

# Variable number of lists of variable length
my @lists = (
   [qw( apple orange tomato )],
   [qw( dog cat platypus )],
   [qw( 1 2 III )],
);
[download]

That's what NestedLoops is for:

local $, = ", ";
local $\ = "\n";
NestedLoops(\@lists, sub { print @_ });
[download]

nFor would require:

local $, = ", ";
local $\ = "\n";
nFor { print map $lists[$_][ $_[$_] ], 0..$#_; } map 0+@$_, @lists;
[download]

Maybe you wouldn't have a problem understanding NestedLoops if it provided a map-ish interface?

sub nested(&@) {
    my $cb = shift;
    NestedLoops(\@_, $cb);
}

local $, = ", ";
local $\ = "\n";
nested { print @_; } @lists;
[download]

Update: Switched initial line to something less rude.

What does that have to do with anything?

Everything!

First: Had I found the NestedLoops() syntax intelligable, I might never have sought my own solution, but as is, I would never have come up with the right syntax to do what you've done.

Second: The application I originally wrote nFor() for needed to be as efficient as possible:

c:\test>junk94
Took 0.557000

c:\test>nfor
Took 0.09644
[download]

Given the very essence of the problems these routines are designed to handle is deeply nested algorithms, that nearly 6x difference can become very significant. Plus, if I need to tweak the function for specific purposes, my code is infinitely simpler to modify than NestedLoops().

Read more... (2 kB)

---

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.

"I'd rather go naked than blow up my ass"

The application I originally wrote nFor() for needed to be as efficient as possible:

So make a module. Don't suggest that the OP use and support that big chunk of complex code.

and your my code is infinitely simpler to modify than NestedLoops().

Really? Unless each level of nesting is the same, nFor degrades to

nFor { print map $lists[$_][ $_[$_] ], 0..$#_; } map 0+@$_, @lists;
[download]

I wrote that and I can't even read it.

For the record, the above modified-out-of-all-recognition post originally contained following which is entirely different in both content and tone:

What does that have to do with anything?

#! perl -slw
use strict;

use Algorithm::Loops qw( NestedLoops );

sub nFor(&@) {
    my $cb = shift;
    NestedLoops([ map [ 0..$_-1 ], @_ ], $cb);
}

my @digits = 1 .. 3;

nFor {
    print join '', @digits[ @_ ];
} ( 3 ) x 4;
[download]

nFor would require:

local $, = ", ";
local $\ = "\n";
nFor { print map $lists[$_][ $_[$_] ], 0..$#_; } map 0+@$_, @lists;
[download]

Baloney! You just like complicated don't you.

All that's needed is the intuative:

my @list1 = qw( apple orange tomato );
my @list2 = qw( dog cat platypus );
my @list3 = qw( 1 2 III );

nFor{
    print join ' ',
        $list1[ $_[0] ],
        $list2[ $_[1] ],
        $list3[ $_[2] ],
} ( 3 ) x 3;
[download]

---

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.

"I'd rather go naked than blow up my ass"

You assume they all have the same number of elements.