# Re: [stack] ck: array operations in joy

## sa@dfa.com — 2003-05-16 21:06:44

    >      {[`a`b`c] [a b +] [a c +] *}

     doh!

    that should have been:

         {[`a`b`c]a b + a c + *}

    and i've improved the life code a bit by adding a method for padding

    the universe with zeros:

    [2 [0 , +:] do]          `edge     def         \ glue 0 to top, left;

    [[|:] map |:]       `mirror   def         \ t -> b, l -> r;

    [2 [edge mirror] do]     `pad            def        \ pad around matrix;

    e.g.

         matrix 10 pad do

    wraps matrix in ten layers of 0.

    , is concat, +: is tolerant transpose, |: is reverse.