(tye)Re: getting my neighbours in an N-dimensional space

[tye]

This version creates a closure that counts in base 3 using "digits" -1, 0, and 1, returning the next neighbor each time it is called. It returns "us" as one of our neighbors.

#!/usr/bin/perl -w
use strict;

use mapcar;

sub neighbors {
    my @coords= @_;
    my @offset= (-1) x @coords;
    return sub {
        my $i= 0;
        return   if  ! @coords;
        my @return= mapcar { $_[0] + $_[1] } \@coords, \@offset;
        while(  1 < ++$offset[$i]  ) {
            $offset[$i]= -1;
            if(  $#offset < ++$i  ) {
                @offset= @coords= ();
                last;
            }
        }
        return @return;
    };
}

my $next= neighbors( 6, 2, -4 );
my @coords;
while(  @coords= $next->()  ) {
    print "( @coords )\n";
}

produces:

( 5 1 -5 )
( 6 1 -5 )
( 7 1 -5 )
( 5 2 -5 )
( 6 2 -5 )
( 7 2 -5 )
( 5 3 -5 )
( 6 3 -5 )
( 7 3 -5 )
( 5 1 -4 )
( 6 1 -4 )
( 7 1 -4 )
( 5 2 -4 )
( 6 2 -4 )
( 7 2 -4 )
( 5 3 -4 )
( 6 3 -4 )
( 7 3 -4 )
( 5 1 -3 )
( 6 1 -3 )
( 7 1 -3 )
( 5 2 -3 )
( 6 2 -3 )
( 7 2 -3 )
( 5 3 -3 )
( 6 3 -3 )
( 7 3 -3 )

This was based on (tye)Re: Finding all Combinations and requires mapcar.

        - tye (but my friends call me "Tye")

[grinder]

Oh well done! This is exactly what I was waffling on about. Except that as it stands, your code returns the point of origin, and the origin can't be a neighbour of itself.
--

g r i n d e r
print@_{sort keys %_},$/if%_=split//,'= & *a?b:e\f/h^h!j+n,o@o;r$s-t%t#u';

[tye]

Yeah, I mentioned that. Here is one that fixes that and is actually simpler. (:

#!/usr/bin/perl -w
use strict;

use mapcar;

sub neighbors {
    my @coords= @_;
    my @digits= ( 0, -1, 1 );
    my @offset= (0) x @coords;
    return sub {
        my $i= 0;
        while(  2 < ++$offset[$i]  ) {
            $offset[$i]= 0;
            return   if  $#offset < ++$i;
        }
        return mapcar { $_[0] + $digits[$_[1]] }
            \@coords, \@offset;
    };
}

my $next= neighbors( 6, 2, -4 );
my @coords;
while(  @coords= $next->()  ) {
    print "( @coords )\n";
}

        - tye (but my friends call me "Tye")