From 18abc8b9f141d6047102acb50a2a16f002ff07ff Mon Sep 17 00:00:00 2001
From: Samuel Tardieu <sam@rfc1149.net>
Date: Mon, 27 Apr 2009 17:23:59 +0200
Subject: [PATCH] Add q+ and q- to math.quaternions

This makes the quaternions library self-contained and more independent
of the underlying representation.
---
 basis/math/quaternions/quaternions-docs.factor  | 10 ++++++++++
 basis/math/quaternions/quaternions-tests.factor |  4 ++++
 basis/math/quaternions/quaternions.factor       |  6 ++++++
 3 files changed, 20 insertions(+)

diff --git a/basis/math/quaternions/quaternions-docs.factor b/basis/math/quaternions/quaternions-docs.factor
index bb34ec8da2..a24011cb7c 100644
--- a/basis/math/quaternions/quaternions-docs.factor
+++ b/basis/math/quaternions/quaternions-docs.factor
@@ -1,6 +1,16 @@
 USING: help.markup help.syntax math math.vectors vectors ;
 IN: math.quaternions
 
+HELP: q+
+{ $values { "u" "a quaternion" } { "v" "a quaternion" } { "u+v" "a quaternion" } }
+{ $description "Add quaternions." }
+{ $examples { $example "USING: math.quaternions prettyprint ;" "{ C{ 0 1 } 0 } { 0 1 } q+ ." "{ C{ 0 1 } 1 }" } } ;
+
+HELP: q-
+{ $values { "u" "a quaternion" } { "v" "a quaternion" } { "u-v" "a quaternion" } }
+{ $description "Subtract quaternions." }
+{ $examples { $example "USING: math.quaternions prettyprint ;" "{ C{ 0 1 } 0 } { 0 1 } q- ." "{ C{ 0 1 } -1 }" } } ;
+
 HELP: q*
 { $values { "u" "a quaternion" } { "v" "a quaternion" } { "u*v" "a quaternion" } }
 { $description "Multiply quaternions." }
diff --git a/basis/math/quaternions/quaternions-tests.factor b/basis/math/quaternions/quaternions-tests.factor
index a6d255e421..3efc417e42 100644
--- a/basis/math/quaternions/quaternions-tests.factor
+++ b/basis/math/quaternions/quaternions-tests.factor
@@ -24,3 +24,7 @@ math.constants ;
 [ t ] [ qk q>v v>q qk = ] unit-test
 [ t ] [ 1 c>q q1 = ] unit-test
 [ t ] [ C{ 0 1 } c>q qi = ] unit-test
+[ t ] [ qi qi q+ qi 2 q*n = ] unit-test
+[ t ] [ qi qi q- q0 = ] unit-test
+[ t ] [ qi qj q+ qj qi q+ = ] unit-test
+[ t ] [ qi qj q- qj qi q- -1 q*n = ] unit-test
diff --git a/basis/math/quaternions/quaternions.factor b/basis/math/quaternions/quaternions.factor
index f2c2c6d226..b713f44ebd 100755
--- a/basis/math/quaternions/quaternions.factor
+++ b/basis/math/quaternions/quaternions.factor
@@ -20,6 +20,12 @@ IN: math.quaternions
 
 PRIVATE>
 
+: q+ ( u v -- u+v )
+    v+ ;
+
+: q- ( u v -- u-v )
+    v- ;
+
 : q* ( u v -- u*v )
     [ q*a ] [ q*b ] 2bi 2array ;