ptfr (PtNode n@(x, lv) lt rt) acc tgt =
    if x == tgt
        then Just n
        else
            if x > tgt
                then acc
                else ptfr lt (jnr acc n) tgt
ptfr (PtNode n@(x, lv) lt rt) acc tgt =
    if x == tgt
        then Just n
        else
            if x > tgt
                then acc
                else ptfr lt (jnr acc n) tgt
ptfr (PtNode n@(x, lv) lt rt) acc tgt =
    if x == tgt
        then Just n
        else
            if x > tgt
                then acc
                else ptfr lt (jnr acc n) tgt