Add vec3::parallel and its test.

1 files changed, 12 insertions, 0 deletions

diff --git a/test_vec.cpp b/test_vec.cpp
index 1c9390f..a81ee09 100644
--- a/test_vec.cpp
+++ b/test_vec.cpp
@@ -117,4 +117,16 @@ TEST(Vec, Refract) {
 TEST(Vec, Refract_TIR) {
     vec3d n{1, 0, 0}, u{-1, 0, -sqrt(3)}, v{1, 0, -sqrt(3)};
     ASSERT_EQ(v.unit_vec(), n.refract<true>(u.unit_vec(), 2));
+}
+
+TEST(Vec, VecParallel) {
+    vec3d a{1, 1, 2}, b{1.1, 1.1, 2.2}, c{0,0,0}, d{1, 2, 1};
+    ASSERT_TRUE(a.parallel(b));
+    ASSERT_TRUE(b.parallel(a));
+    ASSERT_TRUE(a.parallel(c));
+    ASSERT_TRUE(c.parallel(a));
+    ASSERT_FALSE(a.parallel(d));
+    ASSERT_FALSE(d.parallel(a));
+    ASSERT_FALSE(b.parallel(d));
+    ASSERT_FALSE(d.parallel(b));
 }
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