#!/usr/bin/ruby

#
## https://rosettacode.org/wiki/Zig-zag_matrix#Sidef
#

func zig_zag(w, h) {

    var r = [];
    var n = 0;

    h.of { |e|
        w.of { |f|
            [e, f]
        }
    } \
    -> reduce('+') \
    -> sort { |a, b|
           (a[0]+a[1] <=> b[0]+b[1]) ||
           (a[0]+a[1] -> is_even ? a[0]<=>b[0]
                                 : a[1]<=>b[1])
    } \
    -> each { |a|
       r[a[1]][a[0]] = n++;
    }

    return r;
}

zig_zag(5, 5).each {say .join('', {|i| "%4i" % i})};