From 1c23556ef45df23ad14a366ec723700aea78d361 Mon Sep 17 00:00:00 2001
From: Justin Lin <justin.sdk@gmail.com>
Date: Thu, 11 Feb 2021 11:45:28 +0800
Subject: [PATCH] add zipper param

---
 src/util/_impl/_zip_impl.scad | 10 ++++++----
 src/util/zip.scad             |  4 ++--
 test/util/test_zip.scad       |  4 ++++
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/util/_impl/_zip_impl.scad b/src/util/_impl/_zip_impl.scad
index fbcd5462..08504d21 100644
--- a/src/util/_impl/_zip_impl.scad
+++ b/src/util/_impl/_zip_impl.scad
@@ -1,5 +1,7 @@
-function _zipAll_sub(lists, list_to, elem_to, i = 0) = 
-    i > elem_to ? [] :
-    concat([[for(j = [0:list_to]) lists[j][i]]], _zipAll_sub(lists, list_to, elem_to, i + 1));
+_identity = function(elems) elems;
 
-function _zipAll(lists) = _zipAll_sub(lists, len(lists) - 1, len(lists[0]) - 1);
\ No newline at end of file
+function _zipAll_sub(lts, list_to, elem_to, zipper, i = 0) = 
+    i > elem_to ? [] :
+    concat([zipper([for(j = [0:list_to]) lts[j][i]])], _zipAll_sub(lts, list_to, elem_to, zipper, i + 1));
+
+function _zipAll(lts, zipper = _identity) = _zipAll_sub(lts, len(lts) - 1, len(lts[0]) - 1, zipper);
\ No newline at end of file
diff --git a/src/util/zip.scad b/src/util/zip.scad
index a5255457..64ed2753 100644
--- a/src/util/zip.scad
+++ b/src/util/zip.scad
@@ -4,10 +4,10 @@
 * @copyright Justin Lin, 2020
 * @license https://opensource.org/licenses/lgpl-3.0.html
 *
-* @see https://openhome.cc/eGossip/OpenSCAD/lib2x-zip.html
+* @see https://openhome.cc/eGossip/OpenSCAD/lib3x-zip.html
 *
 **/ 
 
 use <_impl/_zip_impl.scad>;
 
-function zip(lts) = _zipAll(lts);
\ No newline at end of file
+function zip(lts, zipper) = is_function(zipper) ? _zipAll(lts, zipper) : _zipAll(lts);
\ No newline at end of file
diff --git a/test/util/test_zip.scad b/test/util/test_zip.scad
index 1cb6da56..0bb20b22 100644
--- a/test/util/test_zip.scad
+++ b/test/util/test_zip.scad
@@ -1,4 +1,5 @@
 use <util/zip.scad>;
+use <util/sum.scad>;
 
 module test_zip() {
     echo("==== test_zip ====");
@@ -8,6 +9,9 @@ module test_zip() {
     zs = [2.5, 7.5, 12.4];
 
     assert(zip([xs, ys, zs]) == [[10, 5, 2.5], [20, 15, 7.5], [30, 25, 12.4]]);
+
+    sum_up = function(elems) sum(elems);
+    assert(zip([xs, ys, zs], sum_up) == [17.5, 42.5, 67.4]);
 }
 
 test_zip();
\ No newline at end of file