Pair

data. Pair

new Pair()

The Pair data type. Pair acts

Version:
  • 3.1.0
Source:
Example
const {Pair} = require('futils').data;

Pair(1, 2); // -> Pair(_1: 1, _2: 2)

Pair(1, 2)._1; // -> 1
Pair(1, 2)._2; // -> 2

Extends

Methods

(static) from(a, b) → {Pair}

Lifts two values into a Pair. This method is curried

Source:
Parameters:
Name Type Description
a any

The first value to lift
b any

The second value to lift
Returns:
Type:
Pair

The values wrapped in a Pair

Example
const {Pair} = require('futils').data;

Pair.from(1, 'a'); // -> Pair(_1: 1, _2: 'a')
Pair.from(1);      // -> a => Pair(_1: 1, _2: a)

(static) fromRight(a, b) → {Pair}

Lifts two values into a Pair from the right. This method is curried

Source:
Parameters:
Name Type Description
a any

The second value to lift
b any

The first value to lift
Returns:
Type:
Pair

The values wrapped in a Pair

Example
const {Pair} = require('futils').data;

Pair.fromRight(1, 'a'); // -> Pair(_1: 'a', _2: 1)
Pair.fromRight(1);      // -> a => Pair(_1: a, _2: 1)

concat(a) → {Pair}

Concatenates a Pair with another. Please note, that the inner values have to be part of a Semigroup as well for concatenation to succeed

Source:
Parameters:
Name Type Description
a Pair

The Pair instance to concatenate with
Returns:
Type:
Pair

A new Pair

Example
const {Pair} = require('futils').data;

const h = Pair('hello', 'how');
const w = Pair('world', 'are you today?');
const s = Pair(' ', ' ');

h.concat(s).concat(w); // -> Pair('hello world', 'how are you today?')

extend(f) → {Pair}

If given a function that takes a Pair and returns a value, returns a Pair

Source:
Parameters:
Name Type Description
f function

A function taking a Pair
Returns:
Type:
Pair

A new Pair

Example
const {Pair} = require('futils').data;

const addFstSnd = ({ _1, _2 }) => _1 + _2;

Pair(1, 1).extend(addFstSnd); // -> Pair(1, 2)

fst() → {any}

Returns the first value of a Pair

Source:
Returns:
Type:
any

The first value of the Pair

Example
const {Pair} = require('futils').data;

Pair(1, 2).fst(); // -> 1

map(f) → {Pair}

Maps a function over the second value of a Pair and returns a new Pair

Source:
Parameters:
Name Type Description
f function

The function to map
Returns:
Type:
Pair

A new Pair

Example
const {Pair} = require('futils').data;

const inc = a => a + 1;

Pair(1, 1).map(inc); // -> Pair(1, 2)

snd() → {any}

Returns the second value of a Pair

Source:
Returns:
Type:
any

The second value of the Pair

Example
const {Pair} = require('futils').data;

Pair(1, 2).snd(); // -> 2