The Rand48 structure implements the C Standard Library
rand48.
As described in the Open Group Specification, these routines work by generating a sequence of 48-bit integer values, \(X_i\), according to the linear congruential formula:
\[ X_{i+1} = (a \cdot X_{i} + c) \mod m \qquad\text{for $i \geq 0$}\]
where
-
\(m = 2^{48}\)
-
\(a = 25214903917\)
-
\(c = 11\)
Synopsis
signature RAND48
structure Rand48 : RAND48Interface
val seed : Word64.word -> Word64.word
val srand : word -> unit
val drand : unit -> real
val lrand : unit -> word
val mrand : unit -> intDescription
val seed : Word64.word -> Word64.word-
seed sinitializes the internal buffer with the 48 low-order bits froms. It returns the previous contents of the buffer. val srand : word -> unit-
srand wsets the internal buffer to(w << 16) | 0x330E. val drand : unit -> real-
drand()returns a random real number in the range \([0..1)\). val lrand : unit -> word-
lrand()returns a unsigned 31-bit random number (i.e., in the range \([0 .. 2^{31}-1\)]). val mrand : unit -> int-
mrand()returns a signed 31-bit random number (i.e., in the range \([-2^{31} .. 2^{31}-1\)]).