universum-1.2.0: Custom prelude used in Serokell

Universum.VarArg

Description

Provides operator of variable-arguments function composition.

Synopsis

# Documentation

class SuperComposition a b c | a b -> c where Source #

This type class allows to implement variadic composition operator.

Minimal complete definition

(...)

Methods

(...) :: 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


#### 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 # Methods(...) :: (a -> b) -> c -> r Source # (SuperComposition (a -> b) d r1, (~) * r (c -> r1)) => SuperComposition (a -> b) (c -> d) r Source # Methods(...) :: (a -> b) -> (c -> d) -> r Source #