Tuple018

The Tuple module was new in Elm 0.18. So, here it is!

first : ( a1, a2 ) -> a1

Extract the first value from a tuple.

first (3, 4) == 3
first ("john", "doe") == "john"

second : ( a1, a2 ) -> a2

Extract the second value from a tuple.

second (3, 4) == 4
second ("john", "doe") == "doe"

mapFirst : (a -> b) -> ( a, a2 ) -> ( b, a2 )

Transform the first value in a tuple.

import String

mapFirst String.reverse ("stressed", 16) == ("desserts", 16)
mapFirst String.length ("stressed", 16) == (8, 16)

mapSecond : (a -> b) -> ( a1, a ) -> ( a1, b )

Transform the second value in a tuple.

import String

mapSecond sqrt ("stressed", 16) == ("stressed", 4)
mapSecond (\x -> x + 1) ("stressed", 16) == ("stressed", 17)

module Tuple018
    exposing
        ( first
        , second
        , mapFirst
        , mapSecond
        )

{-| The `Tuple` module was new in Elm 0.18. So, here it is!

@docs first, second, mapFirst, mapSecond

-}


{-| Extract the first value from a tuple.

    first (3, 4) == 3
    first ("john", "doe") == "john"

-}
first : ( a1, a2 ) -> a1
first =
    fst


{-| Extract the second value from a tuple.

    second (3, 4) == 4
    second ("john", "doe") == "doe"

-}
second : ( a1, a2 ) -> a2
second =
    snd


{-| Transform the first value in a tuple.

    import String

    mapFirst String.reverse ("stressed", 16) == ("desserts", 16)
    mapFirst String.length ("stressed", 16) == (8, 16)

-}
mapFirst : (a -> b) -> ( a, a2 ) -> ( b, a2 )
mapFirst func ( x, y ) =
    ( func x, y )


{-| Transform the second value in a tuple.

    import String

    mapSecond sqrt ("stressed", 16) == ("stressed", 4)
    mapSecond (\x -> x + 1) ("stressed", 16) == ("stressed", 17)

-}
mapSecond : (a -> b) -> ( a1, a ) -> ( a1, b )
mapSecond func ( x, y ) =
    ( x, func y )