in reply to Re: Iterator for multidimensional arrays
in thread Iterator for multidimensional arrays

Almost. A call ->next would return an array of the current 'state' of the system: 
(1,a,A)
(1,a,B)
(1,b,A)
(1,b,B)
(2,a,A)
(2,a,B)
(2,b,A)
(2,b,B)
  • Comment on Re: Re: Iterator for multidimensional arrays

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Re(3): Iterator for multidimensional arrays
by shotgunefx (Parson) on Mar 24, 2002 at 20:43 UTC
    If you want the list generated at once, you could use the following snippet by merlyn. If you want an iterative solution, you could use the following. A benefit being that it should work in relatively constant time no matter how big the arrays are.
    my @aoa = (
    [1,2],
    ['a','b','c','d'],
    ['A','B','C'],
);


my $iter = make_aoa_iterative(@aoa);


while (my @els = $iter->() ){
    print @els,"\n";
}


sub make_aoa_iterative {
    my @arefs = @_;
    my @arrayindexes = ();
    foreach (@arefs){
        push @arrayindexes,[$_,0,$#{$_}];
    }
    
    return sub {
            return if $arrayindexes[0]->[1] > $arrayindexes[0]->[2]; 
            my @els =  map { $_->[0]->[ $_->[1]] } @arrayindexes;
            # Check for out of bounds....
            $arrayindexes[$#arrayindexes]->[1]++;
            for (my $i = $#arrayindexes; $i > 0; $i--){
                    if ($arrayindexes[$i]->[1] > $arrayindexes[$i]->[2
+]){
                        $arrayindexes[$i]->[1] = 0;
                        $arrayindexes[$i-1]->[1]++;
                    }else{
                        last;
                    }
            }
            return @els;
            
    };
}

    [download]
    Update
    I'm formal-math challenged. Is this formally a permutation? If someone could clarify, I'd appreciate it.

    -Lee

    "To be civilized is to deny one's nature."
[reply]
[d/l]
      Yeah... that's does the trick. I had been working on a version that didn't calc all possible indexes beforehand (but now I'll stop). I'll try calling it "a function that returns all possible vectors in a discrete n-dimensional space." It that trekkie enough?
[reply]
        My little test is currently on the 103,000,000th permutation. It would probably be really tough if not impossible to do large sets recursively.

        -Lee

        "To be civilized is to deny one's nature."
[reply]

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