Merge pull request 'set and keep documentation' (#1975) from tyow/localstrudel:composerDocs into main

Reviewed-on: https://codeberg.org/uzu/strudel/pulls/1975

packages/core/pattern.mjs

@@ -1056,7 +1056,55 @@ function _composeOp(a, b, func) {
 
 // pattern composers
 const COMPOSERS = {
+  /**
+   * When called on a pattern `a`, with a input pattern `b` (`a.set(b)`),
+   * combines `a` and `b` such that anything defined in `b`
+   * and anything defined in `a` that is *not* defined in `b`
+   * will be in the resulting pattern.
+   *
+   * The structure is maintained from `a`,
+   * because the default pattern alignment is `in`,
+   * see the section on `Pattern Alignment`
+   * in the technical manual in the docs
+   *
+   * This is the inverse of `keep`
+   *
+   * See examples below
+   * @name set
+   * @param {Pattern} pat
+   * @returns {Pattern}
+   * @memberof Pattern
+   * @tags internal, combiners
+   * @example
+   * // because input pattern has `s` set,
+   * // it overrides the "sine" declared earlier
+   * note("c a f e").s("sine").set(s("triangle"))
+   */
   set: [(a, b) => b],
+  /**
+   * When called on a pattern `a`, with a input pattern `b` (`a.keep(b)`),
+   * combines `a` and `b` such that anything defined in `a`,
+   * and anything defined in `b` that is *not* defined in `a`
+   * will be in the resulting pattern
+   *
+   * The structure is maintained from `a`,
+   * because the default pattern alignment is `in`,
+   * see the section on `Pattern Alignment`
+   * in the technical manual in the docs
+   *
+   * This is the inverse of `set`
+   *
+   * See examples below
+   * @name keep
+   * @param {Pattern} pat
+   * @memberof Pattern
+   * @returns {Pattern}
+   * @tags internal, combiners
+   * @example
+   * // notes, already defined, will stay "c a f e",
+   * // while "s", not defined, will be set to "piano"
+   * note("c a f e").keep(note("e f a c").s("piano"))
+   */
   keep: [(a) => a],
   keepif: [(a, b) => (b ? a : undefined)],