From a7d65e55bde9cd1d1ab34b528acb6588e6b99bed Mon Sep 17 00:00:00 2001
From: Justin Lin <caterpillar@openhome.cc>
Date: Fri, 28 Feb 2020 16:22:16 +0800
Subject: [PATCH] stop if []

---
 .../_impl/_convex_intersection_for_impl.scad           | 10 ++++++----
 src/experimental/convex_intersection.scad              |  1 +
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/experimental/_impl/_convex_intersection_for_impl.scad b/src/experimental/_impl/_convex_intersection_for_impl.scad
index 78e4a48f..b8b4bbc3 100644
--- a/src/experimental/_impl/_convex_intersection_for_impl.scad
+++ b/src/experimental/_impl/_convex_intersection_for_impl.scad
@@ -2,7 +2,9 @@ use <experimental/convex_intersection.scad>;
 
 function _convex_intersection_for(shapes, pre, leng, i = 2) = 
     i == leng ? pre :
-                _convex_intersection_for(shapes, 
-                    convex_intersection(pre, shapes[i]), 
-                    leng, i + 1
-                );
\ No newline at end of file
+    let(r = convex_intersection(pre, shapes[i]))
+    r == [] ? [] 
+            : _convex_intersection_for(shapes, 
+                  r, 
+                  leng, i + 1
+              );
\ No newline at end of file
diff --git a/src/experimental/convex_intersection.scad b/src/experimental/convex_intersection.scad
index f3311815..dc3d2207 100644
--- a/src/experimental/convex_intersection.scad
+++ b/src/experimental/convex_intersection.scad
@@ -4,6 +4,7 @@ use <experimental/_impl/_convex_intersection_impl.scad>;
 use <experimental/convex_ct_clk_order.scad>;
 
 function convex_intersection(shape1, shape2, epsilon = 0.0001) =
+    (shape1 == [] || shape2 == []) ? [] :
     let(
         leng = len(shape1),
         pts = concat(shape1, [shape1[0]])