lib/mlton/basic/fixed-point.sml

   1 (* Copyright (C) 1999-2005 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 structure FixedPoint: FIXED_POINT =
   9 struct
  10
  11 fun fix{start, step, equals} =
  12    let
  13       fun loop s =
  14          let val s' = step s
  15          in if equals(s, s')
  16                then s
  17             else loop s'
  18          end
  19    in loop start
  20    end
  21
  22 fun fix' (f: (unit -> unit) -> unit) =
  23    let
  24       fun loop() =
  25          let val changed = ref false
  26          in f(fn () => changed := true);
  27             if !changed
  28                then loop()
  29             else ()
  30          end
  31    in loop()
  32    end
  33
  34
  35 end