fp2/week2/mart/Random.icl

   1 implementation module Random
   2
   3 import StdFile, StdList, StdMisc, StdArray, Random
   4
   5 :: RandomSeed :== Int
   6
   7 nullRandomSeed :: RandomSeed
   8 nullRandomSeed = 0
   9
  10 getNewRandomSeed :: !*env -> (!RandomSeed, !*env) | FileSystem env
  11 getNewRandomSeed env
  12 # (ok, src, env) = sfopen "/dev/urandom" FReadData env
  13 | not ok => abort "could not open /dev/urandom"
  14 # (bytes, src)   = sfreads src 4
  15   seed           = foldl (\x y->(x<<8)+toInt y) 0 [c \\ c<-:bytes]
  16 | otherwise => (seed, env)
  17
  18 random :: !RandomSeed -> .(!Int, !RandomSeed)
  19 random seed = (seed>>16 bitand 0xFFFF, seed*0x08088405+1)
  20