%!PS

% begin included library code
% see https://codeberg.org/Firedrake/postscript-libraries/
/c.isalpha {
    dup c.islower exch c.isupper or
} bind def

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

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

/c.islower {
    dup 97 ge exch 122 le and
} bind def

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

/a2s {
    2 dict begin
    /i exch def
    i length dup string /o exch def
    1 sub 0 exch 1 exch {
        dup i 3 -1 roll get o 3 1 roll put
    } for
    o
    end
} bind def

/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

/enumerate.array {
    1 dict begin
    /a exch def
    [
      0 1 a length 1 sub {
          [ exch dup a exch get ]
      } for
    ]
    end
} bind def

/c.isupper {
    dup 65 ge exch 90 le and
} bind def

/apush.right { % [a b] c -> [a b c]
    exch
    [ exch aload length 2 add -1 roll ]
} 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


% end included library code

/reverseletters {
    0 dict begin
    s2a /a exch def
    /vout [
        a length {
            32
        } repeat
    ] def
    /letterslots 0 array def
    /letters 0 array def
    a enumerate.array {
        aload pop
        /c exch def
        /i exch def
        c c.isalpha {
            /letterslots letterslots i apush.right def
            /letters letters c apush.right def
        } {
            vout i c put
        } ifelse
    } forall
    letterslots {
        /i exch def
        letters apop.right
        vout exch i exch put
        /letters exch def
    } forall
    vout a2s
    end
} bind def

(reverseletters) test.start
(p-er?l) reverseletters (l-re?p) eq test
(wee-k!L-y) reverseletters (yLk-e!e-w) eq test
(_c-!h_all-en!g_e) reverseletters (_e-!g_nel-la!h_c) eq test
test.end