%!PS

% begin included library code
% see https://codeberg.org/Firedrake/postscript-libraries/
/test {
    /test.count test.count 1 add def
    {
        /test.pass test.pass 1 add def
    } {
        ( ) print
        test.count (....) cvs print
        (-fail) print
    } ifelse
} bind def

/reduce { % array proc -> value
    2 dict begin
    /p exch def
    /a exch def
    a 0 get
    1 1 a length 1 sub {
        a exch get
        p
    } for
    end
} bind def

/reverse {
    1 dict begin
    dup length /l exch def
    [ exch
      aload pop
      2 1 l {
          -1 roll
      } for
    ]
    end
} bind def

/test.end {
    ( ) print
    test.count 0 gt {
        (Passed ) print
        test.pass (...) cvs print
        (/) print
        test.count (...) cvs print
        ( \() print
        test.pass 100 mul test.count idiv (...) cvs print
        (%\)) print
        (\r\n) print
    } if
} bind def

/c.isdigit {
    dup 48 ge exch 57 le and
} bind def

/s2a {
    [ exch { } forall ]
} bind def

/test.start {
    print (:) print
    /test.pass 0 def
    /test.count 0 def
} bind def

/apop.right { % [a b c] -> [a b] c
    [ exch aload length 1 add 1 roll ] exch
} bind def

/map { % array proc -> array
    2 dict begin
    /p exch def
    [ exch
      {
          p
      } forall
    ]
    end
} bind def

/filter { % array proc(bool) -> array
    1 dict begin
    /p exch def
    [ exch
      {
          dup p not
          {
              pop
          } if
      } forall
    ]
    end
} bind def


% end included library code

/luhnalgorithm {
    0 dict begin
    s2a { c.isdigit } filter { 48 sub} map
    apop.right
    /payload exch def
    reverse
    /digits exch def
    0 2 digits length 1 sub {
        digits exch 2 copy get 2 mul
        dup 9 gt {
            9 sub
        } if
        put
    } for
    10 digits { add } reduce 10 mod sub payload eq
    end
} bind def

(luhnalgorithm) test.start
(17893729974) luhnalgorithm test
(4137 8947 1175 5904) luhnalgorithm test
(4137 8974 1175 5904) luhnalgorithm not test
test.end