From c6e0f0533e927a878339a9828c32d21ac9115a7c Mon Sep 17 00:00:00 2001
From: alex <alex@slab.org>
Date: Thu, 11 Dec 2025 23:32:10 +0000
Subject: [PATCH] add delta

---
 packages/core/signal.mjs                  |  9 ++++
 test/__snapshots__/examples.test.mjs.snap | 53 +++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/packages/core/signal.mjs b/packages/core/signal.mjs
index 62fc26ad8..9ac768951 100644
--- a/packages/core/signal.mjs
+++ b/packages/core/signal.mjs
@@ -882,3 +882,12 @@ export const whenKey = register('whenKey', function (input, func, pat) {
 export const keyDown = register('keyDown', function (pat) {
   return pat.fmap(_keyDown);
 });
+
+/**
+ * A pattern that gives the duration of events that are combined with it.
+ * @example
+ * sound("bd sd [bd bd] sd*4 [- sd] [bd [bd bd]]").note(delta.withValue(x => 1/x + 20))
+ */
+export const delta = new Pattern(function (state) {
+  return [new Hap(undefined, state.span, state.span.duration)];
+});
diff --git a/test/__snapshots__/examples.test.mjs.snap b/test/__snapshots__/examples.test.mjs.snap
index 09d285b5d..17dcb08ba 100644
--- a/test/__snapshots__/examples.test.mjs.snap
+++ b/test/__snapshots__/examples.test.mjs.snap
@@ -2784,6 +2784,59 @@ exports[`runs examples > example "delaysync" example index 0 1`] = `
 ]
 `;
 
+exports[`runs examples > example "delta" example index 0 1`] = `
+[
+  "[ 0/1 → 1/6 | s:bd note:26 ]",
+  "[ 1/6 → 1/3 | s:sd note:26 ]",
+  "[ 1/3 → 5/12 | s:bd note:32 ]",
+  "[ 5/12 → 1/2 | s:bd note:32 ]",
+  "[ 1/2 → 13/24 | s:sd note:44 ]",
+  "[ 13/24 → 7/12 | s:sd note:44 ]",
+  "[ 7/12 → 5/8 | s:sd note:44 ]",
+  "[ 5/8 → 2/3 | s:sd note:44 ]",
+  "[ 3/4 → 5/6 | s:sd note:32 ]",
+  "[ 5/6 → 11/12 | s:bd note:32 ]",
+  "[ 11/12 → 23/24 | s:bd note:44 ]",
+  "[ 23/24 → 1/1 | s:bd note:44 ]",
+  "[ 1/1 → 7/6 | s:bd note:26 ]",
+  "[ 7/6 → 4/3 | s:sd note:26 ]",
+  "[ 4/3 → 17/12 | s:bd note:32 ]",
+  "[ 17/12 → 3/2 | s:bd note:32 ]",
+  "[ 3/2 → 37/24 | s:sd note:44 ]",
+  "[ 37/24 → 19/12 | s:sd note:44 ]",
+  "[ 19/12 → 13/8 | s:sd note:44 ]",
+  "[ 13/8 → 5/3 | s:sd note:44 ]",
+  "[ 7/4 → 11/6 | s:sd note:32 ]",
+  "[ 11/6 → 23/12 | s:bd note:32 ]",
+  "[ 23/12 → 47/24 | s:bd note:44 ]",
+  "[ 47/24 → 2/1 | s:bd note:44 ]",
+  "[ 2/1 → 13/6 | s:bd note:26 ]",
+  "[ 13/6 → 7/3 | s:sd note:26 ]",
+  "[ 7/3 → 29/12 | s:bd note:32 ]",
+  "[ 29/12 → 5/2 | s:bd note:32 ]",
+  "[ 5/2 → 61/24 | s:sd note:44 ]",
+  "[ 61/24 → 31/12 | s:sd note:44 ]",
+  "[ 31/12 → 21/8 | s:sd note:44 ]",
+  "[ 21/8 → 8/3 | s:sd note:44 ]",
+  "[ 11/4 → 17/6 | s:sd note:32 ]",
+  "[ 17/6 → 35/12 | s:bd note:32 ]",
+  "[ 35/12 → 71/24 | s:bd note:44 ]",
+  "[ 71/24 → 3/1 | s:bd note:44 ]",
+  "[ 3/1 → 19/6 | s:bd note:26 ]",
+  "[ 19/6 → 10/3 | s:sd note:26 ]",
+  "[ 10/3 → 41/12 | s:bd note:32 ]",
+  "[ 41/12 → 7/2 | s:bd note:32 ]",
+  "[ 7/2 → 85/24 | s:sd note:44 ]",
+  "[ 85/24 → 43/12 | s:sd note:44 ]",
+  "[ 43/12 → 29/8 | s:sd note:44 ]",
+  "[ 29/8 → 11/3 | s:sd note:44 ]",
+  "[ 15/4 → 23/6 | s:sd note:32 ]",
+  "[ 23/6 → 47/12 | s:bd note:32 ]",
+  "[ 47/12 → 95/24 | s:bd note:44 ]",
+  "[ 95/24 → 4/1 | s:bd note:44 ]",
+]
+`;
+
 exports[`runs examples > example "density" example index 0 1`] = `
 [
   "[ 0/1 → 1/4 | s:crackle density:0.01 ]",