Hi,
Does this function remind anybody of anything? It seems like I'm
missing an obvious abstraction:
composeWriter :: [a -> (a, b)] -> a -> (a, [b])
composeWriter [] a
= (a, [])
composeWriter (f:fs) a
= let (a', b) = f a
(final_a, bs) = composeWriter fs a'
in (final_a, b:bs)
It's almost but not quite composition for functions in the Writer
monad; the difference is that every function has exactly one b result,
rather than a list of them.
Edsko
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