Add swap and compose to the Prelude, or Tuple/List

    swap :: (a,b) -> (b,a)
    swap = snd &&& fst

Fairly obvious, but strangely missing.

    compose :: [(a -> a)] -> a -> a
    compose = foldr (.) id

    composeM :: [(a -> m a)] -> a -> m a
    composeM = foldr (<=<) return

This can be done with Endo, of course, but the result is awkward. The idiom of composing a list of endomorphisms occurs often enough that you can Google for it.

Trac metadata

Trac field	Value
Version	7.6.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/base
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