145 lines
2.1 KiB
JavaScript
145 lines
2.1 KiB
JavaScript
import { Algebra, Foldable, Monad, Monoid, Setoid } from './interfaces.js'
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/** @import { Morphism } from './types.js' */
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/** @template T */
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export class Some extends Algebra(Setoid, Monoid, Monad, Foldable) {
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/** @type {T} */
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#value
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/** @param {T} value */
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constructor(value) {
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super()
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this.#value = value
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}
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/**
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* @template T
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* @param {T} value
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* @returns {Some<T>}
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*/
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static of(value) {
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return new Some(value)
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}
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equals(other) {
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return other instanceof Some &&
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other.chain(v => v === this.#value)
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}
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/**
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* @template R
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* @param {Morphism<T, R>} f
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* @returns {R}
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*/
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chain(f) {
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return f(this.#value)
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}
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/**
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* @template R
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* @param {Morphism<T, R>} f
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* @returns {Some<R>}
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*/
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map(f) {
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return Some.of(this.chain(f))
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}
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/**
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* @template R
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* @param {Morphism<T, R>} f
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* @returns {Some<R>}
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*/
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then(f) {
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return this.map(f)
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}
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/**
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* @template U
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* @param {(acc: U, value: T) => U} f
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* @param {U} init
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* @returns {U}
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*/
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reduce(f, init) {
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return f(init, this.#value)
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}
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empty() {
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return Option.empty()
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}
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}
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/** @template T */
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export class None extends Algebra(Setoid, Monoid, Monad, Foldable) {
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equals(other) {
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return other === none
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}
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/**
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* @template R
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* @param {Morphism<T, R>} _f
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* @returns {None}
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*/
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chain(_f) {
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return this
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}
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/**
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* @template R
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* @param {Morphism<T, R>} _f
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* @returns {None}
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*/
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map(_f) {
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return this
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}
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/**
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* @template R
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* @param {Morphism<T, R>} _f
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* @returns {None}
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*/
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then(_f) {
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return this
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}
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/**
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* @template U
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* @param {(acc: U, value: T) => U} _f
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* @param {U} init
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* @returns {U}
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*/
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reduce(_f, init) {
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return init
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}
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empty() {
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return Option.empty()
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}
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}
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/**
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* @template T
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* @type {Some<T> | None<T>} Option
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*/
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export class Option {
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/**
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* @template T
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* @param {T} value
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*/
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static of(value) {
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return Some.of(value)
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}
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static empty() {
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return none
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}
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}
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/**
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* @template T
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* @param {T} value
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*/
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export const some = value => new Some(value)
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export const none = new None()
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