From 823b3399c473e594726023c78eb032e54ba4e89e Mon Sep 17 00:00:00 2001
From: Charles Comstock <dgtized@gmail.com>
Date: Mon, 29 Apr 2024 16:03:48 -0500
Subject: [PATCH] add lcm/gcd as options for c-multiple in helix sketch

---
 src/shimmers/math/core.cljc      | 9 +++++++++
 src/shimmers/sketches/helix.cljs | 6 +++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/shimmers/math/core.cljc b/src/shimmers/math/core.cljc
index 1537c44a3..9e03f5aed 100644
--- a/src/shimmers/math/core.cljc
+++ b/src/shimmers/math/core.cljc
@@ -116,6 +116,15 @@
 
 (comment (map (fn [n] [n (factors n 9)]) (range 1 100)))
 
+;; https://rosettacode.org/wiki/Least_common_multiple#Clojure
+(defn gcd [a b]
+  (if (zero? b)
+    a
+    (recur b (mod a b))))
+
+(defn lcm [a b]
+  (/ (* a b) (gcd a b)))
+
 ;; https://en.wikipedia.org/wiki/Lagrange_polynomial
 ;; https://www.youtube.com/watch?v=4S6G-zenbFM
 (defn lagrange-interpolate [points]
diff --git a/src/shimmers/sketches/helix.cljs b/src/shimmers/sketches/helix.cljs
index 504667453..911d3aca0 100644
--- a/src/shimmers/sketches/helix.cljs
+++ b/src/shimmers/sketches/helix.cljs
@@ -4,6 +4,7 @@
    [shimmers.common.svg :as csvg :include-macros true]
    [shimmers.common.ui.controls :as ctrl]
    [shimmers.common.ui.debug :as debug]
+   [shimmers.math.core :as sm]
    [shimmers.math.deterministic-random :as dr]
    [shimmers.math.equations :as eq]
    [shimmers.math.vector :as v]
@@ -75,7 +76,10 @@
         {:n-points 2048
          :a (* (dr/weighted {-1 1 1 6}) a)
          :b (* (dr/weighted {-1 6 1 1}) b)
-         :c (* (min a b) (dr/random-int 1 6))
+         :c (dr/weighted
+             [[(* (min a b) (dr/random-int 1 6)) 2.0]
+              [(sm/lcm a b) 1.0]
+              [(sm/gcd a b) 1.0]])
          :a-osc (* (dr/random-sign) (dr/random-int 4))
          :b-osc (* (dr/random-sign) (dr/random-int 6))
          :c-osc (* (dr/random-sign) (dr/random-int 12))