lib/mlton/basic/doubly-linked.fun

   1 (* Copyright (C) 1999-2006 Henry Cejtin, Matthew Fluet, Suresh
   2  *    Jagannathan, and Stephen Weeks.
   3  *
   4  * MLton is released under a BSD-style license.
   5  * See the file MLton-LICENSE for details.
   6  *)
   7
   8 functor DoublyLinked(S: DOUBLY_LINKED_STRUCTS): DOUBLY_LINKED =
   9 struct
  10
  11 open S
  12
  13 fun prevp d = #1(destruct d)
  14 fun prev d = Pointer.!(prevp d)
  15 fun setPrev(d,d') = Pointer.:=(prevp d,d')
  16 fun value d = #2(destruct d)
  17 fun nextp d = #3(destruct d)
  18 fun next d = Pointer.!(nextp d)
  19 fun setNext(d,d') = Pointer.:=(nextp d,d')
  20
  21 fun link(d, d') =
  22    (setNext(d, d')
  23     ; setPrev(d',d))
  24
  25 fun insertL(d, d') =
  26    (if Pointer.isNull(prevp d') then () else link(prev d',d)
  27     ; link(d,d'))
  28
  29 fun insertR(d, d') =
  30    (if Pointer.isNull(nextp d) then () else link(d',next d)
  31     ; link(d, d'))
  32
  33 fun unlink d =
  34    (link(prev d,next d)
  35     ; Pointer.clear(prevp d)
  36     ; Pointer.clear(nextp d))
  37
  38 fun isLinked d =
  39    not(Pointer.isNull(prevp d) orelse Pointer.isNull(nextp d))
  40
  41 fun eqPrev(d, d') = Pointer.eq(prevp d, prevp d')
  42
  43 end