Merge pull request #73 from tidalcycles/more-functions

Port `perlin` noise, `rangex`, and `palindrome`

packages/core/pattern.mjs

@@ -311,6 +311,10 @@ export class Pattern {
     return this.mul(max - min).add(min);
   }
 
+  rangex(min, max) {
+    return this.range(Math.log(min), Math.log(max)).fmap(Math.exp);
+  }
+
   // Assumes source pattern of numbers in range -1..1
   range2(min, max) {
     return this._fromBipolar().range(min, max);
@@ -611,6 +615,10 @@ export class Pattern {
     return new Pattern(query)._splitQueries();
   }
 
+  palindrome() {
+    return this.every(2, rev);
+  }
+
   juxBy(by, func) {
     by /= 2;
     const elem_or = function (dict, key, dflt) {

packages/core/signal.mjs

@@ -1,6 +1,7 @@
 import { Hap } from './hap.mjs';
 import { Pattern, fastcat, reify, silence } from './pattern.mjs';
 import Fraction from './fraction.mjs';
+import { id } from './util.mjs';
 
 export function steady(value) {
   // A continuous value
@@ -29,6 +30,8 @@ export const square2 = square._toBipolar();
 export const tri = fastcat(isaw, saw);
 export const tri2 = fastcat(isaw2, saw2);
 
+export const time = signal(id);
+
 // random signals
 
 const xorwise = (x) => {
@@ -75,3 +78,13 @@ export const chooseWith = (pat, xs) => {
 };
 
 export const choose = (...xs) => chooseWith(rand, xs);
+
+export const perlinWith = (pat) => {
+  const pata = pat.fmap(Math.floor);
+  const patb = pat.fmap((t) => Math.floor(t) + 1);
+  const smootherStep = (x) => 6.0 * x ** 5 - 15.0 * x ** 4 + 10.0 * x ** 3;
+  const interp = (x) => (a) => (b) => a + smootherStep(x) * (b - a);
+  return pat.sub(pata).fmap(interp).appBoth(pata.fmap(timeToRand)).appBoth(patb.fmap(timeToRand));
+};
+
+export const perlin = perlinWith(time);

packages/core/util.mjs

@@ -60,6 +60,7 @@ export const removeUndefineds = (xs) => xs.filter((x) => x != undefined);
 export const flatten = (arr) => [].concat(...arr);
 
 export const id = (a) => a;
+export const constant = (a, b) => a;
 
 export const listRange = (min, max) => Array.from({ length: max - min + 1 }, (_, i) => i + min);