haskell - Using System.Random.Mersenne.Pure64 to generate a random Float in the range [0,1] -

i not want use system.random because slower , need generate millions of random floats. cannot use system.random.mwc because not pure.

i made attempt @ writing myself solution not generate uniform range, values close 0.

randomrmsp :: (float,float) -> puremt -> (float,puremt)                    randomrmsp (lo,hi) rng =     let (f,rng') = first double2float (randomdouble rng)     in (lo + f / (maxfloat + 1) * (hi - lo + 1),rng')  maxrealfloat :: realfloat => ->                                            maxrealfloat = encodefloat m n                                               b = floatradix                                                                 e = floatdigits                                                                (_, e') = floatrange                                                           m = b ^ e - 1                                                                    n = e' - e 

i'm pretty sure maxrealfloat function correct because returns correct values floats , doubles according wikipedia

i realized making silly mistake. function randomdouble in system.random.mersenne.pure64 returns double in range [0,1] (which documentation not mention @ all) , consquently numbers small because dividing them max double.