From 84aa43d4606a99bc18d8d32d2506598f9452e970 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 2 May 2014 23:44:59 -0400
Subject: Add transform-position procedure.

* 2d/transform.scm (transform-position): New procedure.
---
 2d/transform.scm | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/2d/transform.scm b/2d/transform.scm
index df2f943..e7b5c31 100644
--- a/2d/transform.scm
+++ b/2d/transform.scm
@@ -33,6 +33,7 @@
             transform-matrix
             transpose
             transform-vector2
+            transform-position
             transform+
             transform*
             transform-translate
@@ -103,6 +104,11 @@ column-major format."
                 (* y (array-ref m 1 1))
                 (array-ref m 1 3)))))
 
+(define (transform-position transform)
+  "Extract 2D vector from TRANSFORM."
+  (let ((m (transform-matrix transform)))
+    (vector2 (array-ref m 0 3) (array-ref m 1 3))))
+
 (define (transform+ . transforms)
   "Return the sum of all given transformation matrices.  Return
 null-transform if called without any arguments."
-- 
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