Safe Haskell | Safe |
---|---|
Language | Haskell2010 |
Provides operator of variable-arguments function composition.
Synopsis
- class SuperComposition a b c | a b -> c where
- (...) :: a -> b -> c
Documentation
class SuperComposition a b c | a b -> c where Source #
This type class allows to implement variadic composition operator.
(...) :: a -> b -> c infixl 8 Source #
Allows to apply function to result of another function with multiple arguments.
>>>
(show ... (+)) 1 2
"3">>>
show ... 5
"5">>>
(null ... zip5) [1] [2] [3] [] [5]
True
Inspired by http://stackoverflow.com/questions/9656797/variadic-compose-function.
Performance
To check the performance there was done a bunch of benchmarks. Benchmarks were made on
examples given above and also on the functions of many arguments.
The results are showing that the operator (...
) performs as fast as
plain applications of the operator (.
) on almost all the tests, but (...
)
leads to the performance draw-down if ghc
fails to inline it.
Slow behavior was noticed on functions without type specifications.
That's why keep in mind that providing explicit type declarations for functions is very
important when using (...
).
Relying on type inference will lead to the situation when all optimizations
disappear due to very general inferred type. However, functions without type
specification but with applied INLINE
pragma are fast again.
Instances
(a ~ c, r ~ b) => SuperComposition (a -> b) c r Source # | |
Defined in Universum.VarArg | |
(SuperComposition (a -> b) d r1, r ~ (c -> r1)) => SuperComposition (a -> b) (c -> d) r Source # | |
Defined in Universum.VarArg |