mlton/atoms/char-size.fun

   1 (* Copyright (C) 2004-2006 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 CharSize (S: CHAR_SIZE_STRUCTS): CHAR_SIZE =
   9 struct
  10
  11 open S
  12
  13 datatype t = C8 | C16 | C32
  14
  15 val all = [C8, C16, C32]
  16
  17 fun bits s =
  18    Bits.fromInt
  19    (case s of
  20        C8 => 8
  21      | C16 => 16
  22      | C32 => 32)
  23
  24 val equals = op =
  25
  26 fun fromBits b =
  27    case Bits.toInt b of
  28       8 => C8
  29     | 16 => C16
  30     | 32 => C32
  31     | _ => Error.bug "CharSize.frombits"
  32
  33 val memoize =
  34    fn f =>
  35    let
  36       val c8 = f C8
  37       val c16 = f C16
  38       val c32 = f C32
  39    in
  40       fn C8 => c8
  41        | C16 => c16
  42        | C32 => c32
  43    end
  44
  45 val cardinality = memoize (fn s => IntInf.pow (2, Bits.toInt (bits s)))
  46
  47 fun isInRange (s, i) = 0 <= i andalso i < cardinality s
  48
  49 end