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 |
Test case | |
Differential revisions | |
BlockedBy | |
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Blocking | |
CC | |
Operating system | |
Architecture |