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Add (&) to Data.Function

    • Closed Issue created by YitzGale @yitzgale

    It is a common idiom to write a sequence of composed combinators in reverse order to the way they would be written with ($) or (.). That naturally expresses the idea of the combinators as operations being applied in the given order.

    This comes up so often, and is commonly used so many times in a single expression, that Control.Arrow.>>> is far too wordy, and even a two-character operator is awkward.

    Surprisingly, until recently the operator (&) was still not used in any of the popular libraries, and its name naturally expresses the idea we are looking for. This operator has now been defined in the lens package. We hereby propose to move it to its natural home for more general use, Data.Function.

    As in the lens package, we define the operator as a flipped version of ($), but with slightly higher precedence for better interaction with ($), and with left associativity. This definition has already proven useful and convenient even in the presence of the large and varied corpus of combinators and operators in the lens package. (There it was formerly known as (%), but that clashed with the usual meaning of (%) from Data.Ratio.)

    infixl 1 &
(&) :: a -> (a -> b) -> b
a & f = f a
{-# INLINE (&) #-}
    Trac metadata
    Trac field Value
    Version 7.6.1
    Type Bug
    TypeOfFailure OtherFailure
    Priority normal
    Resolution Unresolved
    Component libraries/base
    Test case
    Differential revisions
    BlockedBy
    Related
    Blocking
    CC
    Operating system
    Architecture
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