76 lines
2.2 KiB
JavaScript
76 lines
2.2 KiB
JavaScript
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/**
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* A `Magma` is a pair `(A, concat)` in which `A` is a non-empty set and `concat` is a binary operation on `A`
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*
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* See [Semigroup](https://gcanti.github.io/fp-ts/modules/Semigroup.ts.html) for some instances.
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*
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* @since 2.0.0
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*/
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// -------------------------------------------------------------------------------------
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// combinators
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// -------------------------------------------------------------------------------------
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/**
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* The dual of a `Magma`, obtained by swapping the arguments of `concat`.
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*
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* @example
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* import { reverse, concatAll } from 'fp-ts/Magma'
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* import * as N from 'fp-ts/number'
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*
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* const subAll = concatAll(reverse(N.MagmaSub))(0)
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*
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* assert.deepStrictEqual(subAll([1, 2, 3]), 2)
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*
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* @since 2.11.0
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*/
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export var reverse = function (M) { return ({
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concat: function (first, second) { return M.concat(second, first); }
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}); };
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/**
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* @since 2.11.0
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*/
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export var filterFirst = function (predicate) {
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return function (M) { return ({
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concat: function (first, second) { return (predicate(first) ? M.concat(first, second) : second); }
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}); };
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};
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/**
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* @since 2.11.0
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*/
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export var filterSecond = function (predicate) {
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return function (M) { return ({
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concat: function (first, second) { return (predicate(second) ? M.concat(first, second) : first); }
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}); };
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};
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/**
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* @since 2.11.0
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*/
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export var endo = function (f) {
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return function (M) { return ({
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concat: function (first, second) { return M.concat(f(first), f(second)); }
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}); };
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};
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// -------------------------------------------------------------------------------------
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// utils
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// -------------------------------------------------------------------------------------
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/**
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* Given a sequence of `as`, concat them and return the total.
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*
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* If `as` is empty, return the provided `startWith` value.
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*
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* @example
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* import { concatAll } from 'fp-ts/Magma'
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* import * as N from 'fp-ts/number'
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*
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* const subAll = concatAll(N.MagmaSub)(0)
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*
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* assert.deepStrictEqual(subAll([1, 2, 3]), -6)
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*
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* @since 2.11.0
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*/
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export var concatAll = function (M) {
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return function (startWith) {
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return function (as) {
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return as.reduce(function (a, acc) { return M.concat(a, acc); }, startWith);
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};
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};
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};
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