%!PS

% begin included library code
% see https://codeberg.org/Firedrake/postscript-libraries/
/quicksort.cmp {
    2 copy
    lt {
        pop pop -1
    } {
        gt {
            1
        } {
            0
        } ifelse
    } ifelse
} bind def


/quicksort.with_keylist { % [ a c b ] [ keylist ] -> [ a b c ]
    4 dict begin
    /kg exch def
    /arr exch def
    /kl <<
            0 1 arr length 1 sub {
                /i exch def
                arr i get
                kg i get
            } for
        >> def
    arr {
        exch kl exch get exch kl exch get quicksort.cmp
    } quicksort.with_comparator
} bind def

/quicksort.swap {
    2 dict begin
    /bi exch def
    /ai exch def
    arr ai get
    arr bi get
    arr exch ai exch put
    arr exch bi exch put
    end
} bind def

/quicksort {
    { quicksort.cmp } quicksort.with_comparator
} bind def

/quicksort.partition {
    3 dict begin
    /pivot arr hi lo add 2 idiv get def
    /i lo 1 sub def
    /j hi 1 add def
    {
        {
            /i i 1 add def
            arr i get pivot cmp 0 ge {
                exit
            } if
        } loop
        {
            /j j 1 sub def
            arr j get pivot cmp 0 le {
                exit
            } if
        } loop
        i j ge {
            j
            exit
        } if
        i j quicksort.swap
    } loop
    end
} bind def

/quicksort.with_comparator { % [ a c b ] { comparator } -> [ a b c ]
    2 dict begin
    /cmp exch def
    /arr exch def
    arr length 0 gt {
        0 arr length 1 sub quicksort.main
    } if
    arr
    end
} bind def


/quicksort.main { % lo hi -> (null)
    3 dict begin
    /hi exch def
    /lo exch def
    /xit false def
    lo 0 lt {
        /xit true def
    } if
    hi 0 lt {
        /xit true def
    } if
    lo hi ge {
        /xit true def
    } if
    xit not {
        /p quicksort.partition def
        lo p quicksort.main
        p 1 add hi quicksort.main
    } if
    end
} bind def



% end included library code

/shuffle {
    (%Calendar%) currentdevparams /Second get srand
    dup
    [ exch
      length {
          rand
      } repeat
    ]
    quicksort.with_keylist
} bind def

/sixoffortynine {
    [ 1 1 49 { } for ]
    shuffle
    0 6 getinterval
    quicksort
} bind def

sixoffortynine
==