From ba9b7c5b3bda8e3bd215528683a589d40fd8d49e Mon Sep 17 00:00:00 2001
From: Revar Desmera <revarbat@gmail.com>
Date: Sun, 12 May 2019 13:32:34 -0700
Subject: [PATCH] Added product()

---
 math.scad            | 12 ++++++++++++
 tests/test_math.scad | 14 ++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/math.scad b/math.scad
index 8755b15..31a9ab3 100644
--- a/math.scad
+++ b/math.scad
@@ -275,6 +275,18 @@ function sum_of_sines(a, sines) =
 function deltas(v) = len(v)<2? v : [for (p=pair(v)) p.y-p.x];
 
 
+// Function: product()
+// Description:
+//   Returns the product of all entries in the given list.
+//   If passed an array of vectors, returns a vector of products of each part.
+// Arguments:
+//   v = The list to get the product of.
+// Example:
+//   product([2,3,4]);  // returns 24.
+//   product([[1,2,3], [3,4,5], [5,6,7]]);  // returns [15, 48, 105]
+function product(v, i=0, tot=undef) = i>=len(v)? tot : product(v, i+1, ((tot==undef)? v[i] : is_list(v[i])? vmul(tot,v[i]) : tot*v[i]));
+
+
 // Function: mean()
 // Description:
 //   Returns the mean of all entries in the given array.
diff --git a/tests/test_math.scad b/tests/test_math.scad
index 466a564..b8d60a6 100644
--- a/tests/test_math.scad
+++ b/tests/test_math.scad
@@ -253,6 +253,20 @@ module test_sum_of_sines() {
 test_sum_of_sines();
 
 
+module test_deltas() {
+	assert(deltas([2,5,9,17]) == [3,4,8]);
+	assert(deltas([[1,2,3], [3,6,8], [4,8,11]]) == [[2,4,5], [1,2,3]]);
+}
+test_deltas();
+
+
+module test_product() {
+	assert(product([2,3,4]) == 24);
+	assert(product([[1,2,3], [3,4,5], [5,6,7]]) == [15, 48, 105]);
+}
+test_product();
+
+
 module test_mean() {
 	assert(mean([2,3,4]) == 3);
 	assert(mean([[1,2,3], [3,4,5], [5,6,7]]) == [3,4,5]);