aivi.pair

Utilities for working with two-element tuples. Pairs are written (A, B) and are the primary way to group two values of potentially different types.

use aivi.pair (
    fst
    snd
    swap
    mapFst
    mapSnd
    mapBoth
    fromPair
    toPair
    duplicate
)

---

fst

Extracts the first element of a pair.

fst : (A, B) -> A

use aivi.pair (fst)

type (Text, Int) -> Text
func getKey = entry =>
    fst entry

---

snd

Extracts the second element of a pair.

snd : (A, B) -> B

use aivi.pair (snd)

type (Text, Int) -> Int
func getValue = entry =>
    snd entry

---

swap

Swaps the two elements of a pair, returning (B, A) from (A, B).

swap : (A, B) -> (B, A)

use aivi.pair (swap)

type (Text, Int) -> (Int, Text)
func flipEntry = entry =>
    swap entry

---

mapFst

Applies a function to the first element, leaving the second unchanged.

mapFst : (A -> C) -> (A, B) -> (C, B)

use aivi.pair (mapFst)

use aivi.math (square)

type (Int, Text) -> (Int, Text)
func squareFst = pair =>
    mapFst square pair

---

mapSnd

Applies a function to the second element, leaving the first unchanged.

mapSnd : (B -> C) -> (A, B) -> (A, C)

use aivi.pair (mapSnd)

use aivi.math (abs)

type (Text, Int) -> (Text, Int)
func absValue = entry =>
    mapSnd abs entry

---

mapBoth

Applies one function to the first element and another to the second.

mapBoth : (A -> C) -> (B -> D) -> (A, B) -> (C, D)

use aivi.pair (mapBoth)

use aivi.math (
    abs
    negate
)

type (Int, Int) -> (Int, Int)
func normalizePair = pair =>
    mapBoth abs negate pair

---

fromPair

Constructs a pair from two separate values.

fromPair : A -> B -> (A, B)

use aivi.pair (fromPair)

type Text -> Int -> (Text, Int)
func makeEntry = label score =>
    fromPair label score

---

toPair

Constructs a pair from two separate values. Useful as a named combinator when pairing results in a pipeline.

toPair : A -> B -> (A, B)

use aivi.pair (toPair)

type Text -> Int -> (Text, Int)
func labelScore = label score =>
    toPair label score

---

duplicate

Creates a pair where both elements are the same value.

duplicate : A -> (A, A)

use aivi.pair (duplicate)

type Int -> (Int, Int)
func mirror = n =>
    duplicate n