doc/guide/src/MLtonIntInf.adoc

   1 MLtonIntInf
   2 ===========
   3
   4 [source,sml]
   5 ----
   6 signature MLTON_INT_INF =
   7    sig
   8       type t = IntInf.int
   9
  10       val areSmall: t * t -> bool
  11       val gcd: t * t -> t
  12       val isSmall: t -> bool
  13
  14       structure BigWord : WORD
  15       structure SmallInt : INTEGER
  16       datatype rep =
  17          Big of BigWord.word vector
  18        | Small of SmallInt.int
  19       val rep: t -> rep
  20       val fromRep : rep -> t option
  21    end
  22 ----
  23
  24 MLton represents an arbitrary precision integer either as an unboxed
  25 word with the bottom bit set to 1 and the top bits representing a
  26 small signed integer, or as a pointer to a vector of words, where the
  27 first word indicates the sign and the rest are the limbs of a
  28 <:GnuMP:> big integer.
  29
  30 * `type t`
  31 +
  32 the same as type `IntInf.int`.
  33
  34 * `areSmall (a, b)`
  35 +
  36 returns true iff both `a` and `b` are small.
  37
  38 * `gcd (a, b)`
  39 +
  40 uses the <:GnuMP:GnuMP's> fast gcd implementation.
  41
  42 * `isSmall a`
  43 +
  44 returns true iff `a` is small.
  45
  46 * `BigWord : WORD`
  47 +
  48 representation of a big `IntInf.int` as a vector of words; on 32-bit
  49 platforms, `BigWord` is likely to be equivalent to `Word32`, and on
  50 64-bit platforms, `BigWord` is likely to be equivalent to `Word64`.
  51
  52 * `SmallInt : INTEGER`
  53 +
  54 representation of a small `IntInf.int` as a signed integer; on 32-bit
  55 platforms, `SmallInt` is likely to be equivalent to `Int32`, and on
  56 64-bit platforms, `SmallInt` is likely to be equivalent to `Int64`.
  57
  58 * `datatype rep`
  59 +
  60 the underlying representation of an `IntInf.int`.
  61
  62 * `rep i`
  63 +
  64 returns the underlying representation of `i`.
  65
  66 * `fromRep r`
  67 +
  68 converts from the underlying representation back to an `IntInf.int`.
  69 If `fromRep r` is given anything besides the valid result of `rep i`
  70 for some `i`, this function call will return `NONE`.