[Haskell-cafe] Practical use of Stream's monad instance?
olf at aatal-apotheke.de
Mon Jul 11 20:10:43 UTC 2016
As someone else on this list whose name I don't recall put it, there is no
choice on whether to make Stream a monad or not. It simply _is_ a monad.
Anyone with some CS education hearing 'diagonal of inifinite list of
infinite lists' should immediately think of Georg Cantor.
type Real = Stream Rational
-- approximate a real number by an ascending stream
-- of lower bounds.
supremum :: Stream Real -> Real
supremum = join
-- If a stream of reals is index-wise ascending,
-- the monad instance for Stream computes its supremum.
-- Use this e.g. to compute any mathematical quantity
-- defined as a supremum.
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