#!/usr/bin/perl

use Data::Dumper;

my $max=10;


### Straight forward


sub list (&){
    my $code_ref=shift;
    &$code_ref;
    return @_;
}


@x= list { for $c (1..10){ for $b (1..$c){ for $a (1..$b){
           push @_, [$c,$b,$a]  if $c**2 == $b**2 + $a**2;
    } } } };

print Dumper \@x;



### ist das pushen zu haesslich?

{
    my @list;

    sub gather (&){
        my $code_ref=shift;
        
        @list=();                          # KORRIGIERT:  danke Matthias W.
        &$code_ref;
        return @list;
    }

    sub take ($) {
        my $elem = shift;
        push @list, $elem;
        return;
    }
}



@x= gather {
    for $c (1..10){   for $b (1..$c){   for $a (1..$b){  if ( $c**2 == $b**2 + $a**2){
        take [$c,$b,$a]
    } } } }
};

print Dumper \@x;




### lazy evaluation ?




{
    my ($a,$b,$c)=(0,0,0);

    sub lazy {
        while ( $c++ < $max ) {
            while ( $b++ < $c ) {
                while ( $a++, $a %= $b ) {
                    return [$c,$b,$a] if $c**2 == $b**2 + $a**2;
                };
                # $a=0; # unnötig
            };
            $b=0;
        }
        $c=0;
        return;
    }
}





while ( $triple = lazy() ) {
    print Dumper $triple;
}