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ryuta-ito/cardinality.hs

Created January 14, 2017 06:15
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cardinality.hs
-- N^2 ~ N
f (x, y) = (((x+y)*(x+y+1))/2) + x + 1
a n = b (0, n)
b (x, 0) = [(x, 0)]
b (x, y) = (x, y) : b (x+1, y-1)
app n = map f ([0..n] >>= a)
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-- Z ~ N
a 0 = [0]
a n = (a (n-1)) ++ [n, (n*(-1))]
f n  = if n > 0 then n*2 else n*(-1)*2+1

app n = map f (a n)

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