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add pipe + compose

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This commit is contained in:
Felix Roos 2022-04-11 22:31:02 +02:00
parent 3f603eb84f
commit de3c453763
2 changed files with 25 additions and 1 deletions
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15
packages/core/test/util.test.mjs
View File

@ -1,5 +1,5 @@
import { strict as assert } from 'assert';
import { isNote, tokenizeNote, toMidi, mod } from '../util.mjs';
import { isNote, tokenizeNote, toMidi, mod, compose } from '../util.mjs';
describe('isNote', () => {
it('should recognize notes without accidentals', () => {
@ -83,3 +83,16 @@ describe('mod', () => {
assert.equal(mod(-3, 2), 1);
});
});
describe('compose', () => {
const add1 = (a) => a + 1;
it('should compose', () => {
assert.equal(compose(add1, add1)(0), 2);
assert.equal(compose(add1)(0), 1);
});
const addS = (s) => (a) => a + s;
it('should compose left to right', () => {
assert.equal(compose(addS('a'), addS('b'))(''), 'ab');
assert.equal(compose(addS('a'), addS('b'))('x'), 'xab');
});
});

11
packages/core/util.mjs
View File

@ -42,3 +42,14 @@ export const getPlayableNoteValue = (event) => {
// rotate array by n steps (to the left)
export const rotate = (arr, n) => arr.slice(n).concat(arr.slice(0, n));
export const pipe = (...funcs) => {
return funcs.reduce(
(f, g) =>
(...args) =>
f(g(...args)),
(x) => x,
);
};
export const compose = (...funcs) => pipe(...funcs.reverse());