lib/mlton/basic/control.fun

   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 functor Control(): CONTROL =
   9 struct
  10
  11 val defaults: (unit -> unit) list ref = ref []
  12
  13 val settings: {name: string,
  14                value: (unit -> string)} list ref = ref []
  15
  16 fun setDefaults() = List.foreach(!defaults, fn f => f())
  17
  18 fun control{name, default, toString} =
  19    let val r = ref default
  20    in List.push(settings, {name = name,
  21                            value = fn () => toString(!r)})
  22       ; List.push(defaults, fn () => r := default)
  23       ; r
  24    end
  25
  26 fun all() =
  27    List.fold(!settings, [], fn ({name, value}, ac) =>
  28              {name = name, value = value()} :: ac)
  29
  30 end