[Haskell-cafe] more improvable randomness
mpm at alumni.caltech.edu
Thu Oct 8 11:38:46 EDT 2009
I wrote some code to model the keystroke-to-keystroke delay in a person
typing, with pseudorandomness. There are two kinds of delays.. one is a
very small delay as the person reaches for a new key (call this 'reach'
delays), the other is a larger delay that represents a pause to think or
to take a break (call this 'break' delays).
My thought is that I could create an infinite series of reach delays and
an infinite series of break delays and zipWith (+).
The inifinite series of break delays would look like:
- The overall pattern is a large number of zeros, in the range (N,M)
followed by a single positive number, chosen from a distribution D... and
Here's some code. I used the Gen monad to gain access to the 'frequency'
function, which is useful, but I had trouble figuring out how to put the
whole algorithm into Gen. I also looked at Rand. The problem is that if I
want to create the list by 'sequence'ing a list of monads, they need to
have state that remembers how many zeros are left to go.
breakSeries :: Int -> Int -> StdGen -> [Float]
breakSeries lowerB upperB gen =
let (n,gen1) = randomR (lowerB,upperB) gen
(gen2,gen3) = split gen1
delay = generate 1 gen2 breakM
in replicate n 0 ++ [delay] ++ breakSeries lowerB upperB gen3
breakM :: Gen Float
breakM = frequency [ (10, choose( 1::Float , 2))
, (10, choose( 4::Float , 6)) ]
test = (print . take 100 . breakSeries 2 4 ) =<< newStdGen
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