optimise euclidish, creating new morph function in the process

packages/core/euclid.mjs

@@ -10,7 +10,7 @@ https://rohandrape.net/?t=hmt
 This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details. You should have received a copy of the GNU Affero General Public License along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
-import { timeCat, register, silence, stack, pure } from './pattern.mjs';
+import { timeCat, register, silence, stack, pure, _morph } from './pattern.mjs';
 import { rotate, flatten, splitAt, zipWith } from './util.mjs';
 import Fraction, { lcm } from './fraction.mjs';
 
@@ -212,22 +212,10 @@ export const euclidLegatoRot = register(['euclidLegatoRot'], function (pulses, s
  * @param {number} steps the number of steps to fill
  * @param {number} groove exists between the extremes of 0 (straight euclidian) and 1 (straight pulse)
  * @example
- * sound("hh").euclidish(7,12,tri.slow(8))
- * .pan(tri.slow(8))
+ * sound("hh").euclidish(7,12,sine.slow(8))
+ * .pan(sine.slow(8))
  */
 export const { euclidish, eish } = register(['euclidish', 'eish'], function (pulses, steps, perc, pat) {
-  const b = bjork(pulses, steps);
-  let trues = 0;
-  const offs = [];
-  for (const [pos, step] of b.entries()) {
-    if (step) {
-      offs.push([trues++, pos]);
-    }
-  }
-  const tweened = offs.map(([n, pos]) =>
-    Fraction(pos)
-      .div(steps)
-      .add(Fraction(n).div(pulses).sub(Fraction(pos).div(steps)).mul(perc)),
-  );
-  return pat.struct(stack(...tweened.map((pos) => pure(true)._fastGap(steps)._late(pos)))).setSteps(steps);
+  const morphed = _morph(bjork(pulses, steps), new Array(pulses).fill(1), perc);
+  return pat.struct(morphed).setSteps(steps);
 });

packages/core/pattern.mjs

@@ -21,6 +21,7 @@ import {
   numeralArgs,
   parseNumeral,
   pairs,
+  zipWith,
 } from './util.mjs';
 import drawLine from './drawLine.mjs';
 import { logger } from './logger.mjs';
@@ -3400,3 +3401,69 @@ export const { beat } = register(
   ['beat'],
   __beat((x) => x.innerJoin()),
 );
+
+export const _morph = (from, to, by) => {
+  by = Fraction(by);
+  const dur = Fraction(1).div(from.length);
+  const positions = (list) => {
+    const result = [];
+    for (const [pos, value] of list.entries()) {
+      if (value) {
+        result.push([Fraction(pos).div(list.length), value]);
+      }
+    }
+    return result;
+  };
+  const arcs = zipWith(
+    ([posa, valuea], [posb, valueb]) => {
+      const b = by.mul(posb - posa).add(posa);
+      const e = b.add(dur);
+      return new TimeSpan(b, e);
+    },
+    positions(from),
+    positions(to),
+  );
+  function query(state) {
+    const cycle = state.span.begin.sam();
+    const cycleArc = state.span.cycleArc();
+    const result = [];
+    for (const whole of arcs) {
+      const part = whole.intersection(cycleArc);
+      if (part !== undefined) {
+        result.push(
+          new Hap(
+            whole.withTime((x) => x.add(cycle)),
+            part.withTime((x) => x.add(cycle)),
+            true,
+          ),
+        );
+      }
+    }
+    return result;
+  }
+  return new Pattern(query).splitQueries();
+};
+
+/**
+ * Takes two binary rhythms represented as lists of 1s and 0s, and a number
+ * between 0 and 1 that morphs between them. The two lists should contain the same
+ * number of true values.
+ * @example
+ * sound("hh").struct(morph([1,0,1,0,1,0,1,0], // straight rhythm
+ *                          [1,1,0,1,0,1,0], // wonky rhythm
+ *                          0.25 // creates a slightly wonky rhythm
+ *                         )
+ *                   )
+ * @example
+ * sound("hh").struct(morph("1:0:1:0:1:0:1:0", // straight rhythm
+ *                          "1:1:0:1:0:1:0", // wonky rhythm
+ *                          sine.slow(8) // slowly morph between the rhythms
+ *                         )
+ *                   )
+ */
+export const morph = (frompat, topat, bypat) => {
+  frompat = reify(frompat);
+  topat = reify(topat);
+  bypat = reify(bypat);
+  return frompat.innerBind((from) => topat.innerBind((to) => bypat.innerBind((by) => _morph(from, to, by))));
+};

packages/core/timespan.mjs

@@ -72,7 +72,7 @@ export class TimeSpan {
   }
 
   intersection(other) {
-    // Intersection of two timespans, returns None if they don't intersect.
+    // Intersection of two timespans, returns undefined if they don't intersect.
     const intersect_begin = this.begin.max(other.begin);
     const intersect_end = this.end.min(other.end);