Add parallel composition

2 files changed, 51 insertions, 3 deletions

diff --git a/src/unheard/cycles.clj b/src/unheard/cycles.clj
index 513b090..5511d64 100644
--- a/src/unheard/cycles.clj
+++ b/src/unheard/cycles.clj
@@ -29,6 +29,20 @@
   [& args]
   {:v (vec args) :type :f})
 
+(defn p
+  "Parallel combinator: all children occur simultaneously.
+
+  Each child gets the full time duration of the parent.
+  All children are active at the same time, producing overlapping intervals.
+
+  Equivalent to TidalCycles/Strudel 'stack' operator.
+
+  Example:
+    (p :a :b :c) with cycle-length 1
+    => [[0 1 :a] [0 1 :b] [0 1 :c]]"
+  [& args]
+  {:v (vec args) :type :p})
+
 (defn scalar? [x]
   (not (and (map? x) (:type x))))
 
@@ -49,6 +63,10 @@
 
     (= :l (:type node))
     (let [children (:v node)]
+      (reduce lcm 1 (map compute-cycle children)))
+
+    (= :p (:type node))
+    (let [children (:v node)]
       (reduce lcm 1 (map compute-cycle children)))))
 
 (defn unfold-node [node start end iteration]
@@ -72,7 +90,13 @@
       (let [children (:v node)
             n (count children)
             child-idx (mod iteration n)]
-        (unfold-node (nth children child-idx) start end (quot iteration n))))))
+        (unfold-node (nth children child-idx) start end (quot iteration n)))
+
+      (= :p (:type node))
+      (let [children (:v node)]
+        (mapcat (fn [child]
+                  (unfold-node child start end iteration))
+                children)))))
 
 (defn unfold
   "Unfolds a pattern tree into concrete time intervals.
diff --git a/test/unheard/cycles_test.clj b/test/unheard/cycles_test.clj
index b912895..ef9aca7 100644
--- a/test/unheard/cycles_test.clj
+++ b/test/unheard/cycles_test.clj
@@ -1,6 +1,6 @@
 (ns unheard.cycles-test
   (:require [clojure.test :refer [deftest is testing]]
-            [unheard.cycles :refer [l f unfold]]))
+            [unheard.cycles :refer [l f p unfold]]))
 
 (deftest unfold-tests
   (testing "single scalar"
@@ -62,4 +62,28 @@
   (testing "fork with nested list subdivides correctly"
     (is (= [[0 1/3 :a] [1/3 2/3 :b] [2/3 1 :c]
             [1 2 :x]]
-           (unfold 1 (f (l :a :b :c) :x))))))
+           (unfold 1 (f (l :a :b :c) :x)))))
+
+  (testing "simple parallel - all children at same time"
+    (is (= [[0 1 :a] [0 1 :b] [0 1 :c]]
+           (unfold 1 (p :a :b :c)))))
+
+  (testing "parallel with list - children subdivide in parallel"
+    (is (= [[0 1/2 :a] [1/2 1 :b]
+            [0 1/2 :c] [1/2 1 :d]]
+           (unfold 1 (p (l :a :b) (l :c :d))))))
+
+  (testing "parallel with fork - forks extend together"
+    (is (= [[0 1 :a] [0 1 :c]
+            [1 2 :b] [1 2 :d]]
+           (unfold 1 (p (f :a :b) (f :c :d))))))
+
+  (testing "list containing parallel"
+    (is (= [[0 1/2 :x] [0 1/2 :y]
+            [1/2 1 :z]]
+           (unfold 1 (l (p :x :y) :z)))))
+
+  (testing "parallel with different cycle lengths"
+    (is (= [[0 1 :a] [0 1 :b]
+            [1 2 :a] [1 2 :c]]
+           (unfold 1 (p :a (f :b :c)))))))