moy-fp/test/Function/flip.test.js

A functional programming library.

import __ from '../../src/Function/__'
/**
 * ((a, b, ..., m) -> n) -> ((b, a, ..., m) -> n)
 */
import flip from '../../src/Function/flip'

test('flip(not using __), the original arity is 1', () => {
  expect(
    flip(a => [a])(1)
  ).toEqual([undefined])
})

test('flip(not using __), the original arities are 2', () => {
  expect(
    flip((a, b) => [a, b])(1)(2)
  ).toEqual([2, 1])
})


test('flip(not using __), the original arities are 3', () => {
  expect(
    flip((a, b, c) => [a, b, c])(1)(2)(3)
  ).toEqual([2, 1, 3])
})

test('flip(using __), the original arity is 2', () => {
  expect(
    flip(__)((a, b) => [a, b])(1)(2)
  ).toEqual([2, 1])
})