From 37359e1b6de63d5434112364c1301f8202a7cfdc Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sun, 12 Nov 2017 21:41:10 -0500
Subject: math: quaternion: Add custom record type printer.

* chickadee/math/quaternion.scm (display-quaternion): New procedure.
---
 chickadee/math/quaternion.scm | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/chickadee/math/quaternion.scm b/chickadee/math/quaternion.scm
index 4df4ffd..cf2b4bc 100644
--- a/chickadee/math/quaternion.scm
+++ b/chickadee/math/quaternion.scm
@@ -23,7 +23,9 @@
 
 (define-module (chickadee math quaternion)
   #:use-module (chickadee math)
+  #:use-module (ice-9 format)
   #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-9 gnu)
   #:use-module (system foreign)
   #:export (quaternion
             quaternion?
@@ -88,6 +90,15 @@
   "Return the W coordinate of the quaternion Q."
   (quaternion-ref q 3))
 
+(define (display-quaternion q port)
+  (format port "#<quaterion ~f ~f ~f ~f>"
+          (quaternion-x q)
+          (quaternion-y q)
+          (quaternion-z q)
+          (quaternion-w q)))
+
+(set-record-type-printer! <quaternion> display-quaternion)
+
 (define-inlinable (quaternion-magnitude q)
   "Return the magnitude of the quaternion Q."
   (sqrt
-- 
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