[Haskell-cafe] Generating random tuples
jacek.generowicz at cern.ch
Mon Nov 1 14:18:33 EDT 2010
I'm toying with generating random objects (for example tuples) and
started wondering what pearls of wisdom Cafe might have on the matter.
Two obvious points (relating to my toy code, shown below) are
1) The meaning of the limits required by randomR is not obvious for
types such as tuples (you could come up with some definition, but it
wouldn't be unique: how would you allow for different ones?[*]; you
might decide that having such limits is nonsensical and not want to
provide a randomR: would you then leave it undefinded?).
[*] I guess this is related to issues such as Num being both a sum and
and product monoid.
2) I'm sure there are at least half a dozen prettier definitions of
But I suspect that the juicy bits will be in offerings about issues
that I haven't even dreamed about.
Presumably QuickCheck's test-data generation mechanism would be
interesting to look at in this context. Is there a gentle explanation
of how it works somewhere?
Here's my initial effort:
main :: IO (Int, Int)
main = randomIO
instance (Random a, Random b) => Random (a, b) where
randomR = undefined
random g0 = let (i1,g1) = random g0
(i2,g2) = random g1
in ((i1,i2), g1)
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