%!PS

/aeq {
    2 dict begin
    /a exch def
    /b exch def
    a length b length eq {
        /e true def
        0 1 a length 1 sub {
            dup a exch get
            exch b exch get ne {
                /e false def
                exit
            } if
        } for
        e
    } {
        false
    } ifelse
    end
} bind def

/apush { % [a b] c -> [a b c]
    /t exch def
    [ exch aload pop t ]
} bind def

/spush { % (ab) c -> (abc)
    3 dict begin
    /t exch 0 get def
    /a exch def
    a length 1 add string /b exch def
    a b copy pop
    b b length 1 sub t put
    b
    end
} bind def

/i2s {
    dup log cvi 1 add string cvs
} bind def

/stringify {
    exch i2s 0 string exch spush
    (/) spush
    exch i2s spush
} bind def

/get_parent {
    2 copy
    gt {
        exch 1 index sub exch
    } {
        1 index sub
    } ifelse
} bind def

/p_gp {
    /out 0 array def
    (/) search {
        cvi
        exch pop
        exch cvi
        1 1 2 {
            pop get_parent 2 copy stringify out exch apush /out exch def
        } for
        out
    } {
        pop out
    } ifelse
} bind def

(3/5) p_gp [ (3/2) (1/2) ] aeq { (Pass) } { (FAIL) } ifelse print ( ) print
(4/3) p_gp [ (1/3) (1/2) ] aeq { (Pass) } { (FAIL) } ifelse =