From fb77b7288ce5406ff819d8fd71ad59e317d1817f Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <rmlarsen@google.com>
Date: Thu, 9 Jul 2020 12:49:58 -0700
Subject: Add operator<< to print a quaternion.

---
 Eigen/src/Geometry/Quaternion.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

(limited to 'Eigen/src/Geometry')

diff --git a/Eigen/src/Geometry/Quaternion.h b/Eigen/src/Geometry/Quaternion.h
index dd1217e5e..bebfca422 100644
--- a/Eigen/src/Geometry/Quaternion.h
+++ b/Eigen/src/Geometry/Quaternion.h
@@ -197,20 +197,25 @@ class QuaternionBase : public RotationBase<Derived, 3>
   #else
 
   template<typename NewScalarType>
-  EIGEN_DEVICE_FUNC inline 
+  EIGEN_DEVICE_FUNC inline
   typename internal::enable_if<internal::is_same<Scalar,NewScalarType>::value,const Derived&>::type cast() const
   {
     return derived();
   }
 
   template<typename NewScalarType>
-  EIGEN_DEVICE_FUNC inline 
+  EIGEN_DEVICE_FUNC inline
   typename internal::enable_if<!internal::is_same<Scalar,NewScalarType>::value,Quaternion<NewScalarType> >::type cast() const
   {
     return Quaternion<NewScalarType>(coeffs().template cast<NewScalarType>());
   }
   #endif
 
+  friend std::ostream& operator<<(std::ostream& s, const QuaternionBase<Derived>& q) {
+    s << q.x() << "i + " << q.y() << "j + " << q.z() << "k" << " + " << q.w();
+    return s;
+  }
+
 #ifdef EIGEN_QUATERNIONBASE_PLUGIN
 # include EIGEN_QUATERNIONBASE_PLUGIN
 #endif
-- 
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