Tuple

Some helpers for working with 2-tuples.

Note: For larger chunks of data, it is best to switch to using records. So instead of representing a 3D point as (3,4,5) and wondering why there are no helper functions, represent it as { x = 3, y = 4, z = 5 } and use all the built-in syntax for records.

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)

elm-lang/core/5.1.1

Tuple

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