#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;
use Carp;

sub gen_triangles {
    my $max = shift || 10;
    my @set;
    
    for my $c (1..$max) {
        for my $b (1..$c) {
            for my $a (1..$b) {
                push @set, [$a, $b, $c] if $c**2 == $b**2 + $a**2;
            }
        }
    }    
    return \@set;
}

print Dumper gen_triangles;

print [(a,b,c) for c in range(20) for b in range(c) for a in range(b) if c**2==a**2+b**2]

let triangles = [ (a, b ,c) | c <- [1..], b <- [1..c], a <- [1..b], a^2+b^2==c^2 ]
take 10 triangles

my @pyt = gather {
   for 1..20 -> $c {
       for 1..$c -> $b {
           my $a = sqrt($c**2 - $b**2);
           take [$a, $b, $c] if $a == int($a);
       }
   }
}

for $c (1..10) { for $b (1..$c) { for $a (1..$b) {
    print $c,$b,$a  if $c**2 == $b**2 + $a**2;
} } }

sub gen_triangles {
  my $max = shift || 10;
  my @set;
  my($x,$y,$z)=(1,1,1);
  while($z<=$max && $x<=$max){
    push @set, [$z, $y, $x] if $x**2 == $y**2 + $z**2;
    if($y>$z){$z++}else{if($x>$y){$y++;$z=1}else{$x++;$y=$z=1}}
  }
  return \@set;
}

#!/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;
}