33 lines
704 B
JavaScript
33 lines
704 B
JavaScript
import { it, assertEq } from 'folktest'
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import { Monad } from '../../src/monad.js'
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const leftIdentity = (M, a, f) => {
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assertEq(M(a).bind(f), f(a))
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}
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const rightIdentity = (M, m) => {
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assertEq(m.bind(M), m)
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}
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const associativity = (m, f, g) => {
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assertEq(m.bind(f).bind(g), m.bind(x => f(x).bind(g)))
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}
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export const prove = (M, m, a, f, g) => {
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leftIdentity(M, a, f)
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rightIdentity(M, m)
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associativity(m, f, g)
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}
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export const Tests = [
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it('should adhere to monadic laws', () => {
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const ctr = Monad.bind(undefined, Monad)
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prove(
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ctr,
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ctr(1),
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1,
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x => ctr(x + 1),
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x => ctr(x * 2)
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)
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})
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]
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