Op 8-10-2015 om 01:16 schreef Richard A. O'Keefe:
You can generate two unequal integers by doing
prop_twoDifferent :: Int -> Int -> Bool prop_twoDifferent x y = yourFn2 x y' where y' = if y >= x then y+1 else y
Letting the number of distinct Int values be N, there are N*N pairs of Ints but only N*(N-1) pairs of *different* Ints, so this technique will generate some x y' pairs more often than others. In fact you will get (x,minBound::Int) with probability 2/N and (x,y>minBound) with probability 1/N. The advantage of using a guard is that the probabilities come out right (it's the "rejection method", in statistical parlance).
You can use that method to generate x x y x y x y x x
You can iterate the same idea to generate triples.
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Thanks all. Enough to study and try. Roelof