Math: added Vector::lengthInverted().

Also because there are SIMD instructions for that.

src/Math/Functions.h

@@ -219,7 +219,7 @@ template<std::size_t size, class T> Vector<size, T> sqrt(const Vector<size, T>&
 /**
 @brief Inverse square root
 
-@see sqrt()
+@see sqrt(), Vector::lengthInverted()
 */
 #ifdef DOXYGEN_GENERATING_OUTPUT
 template<class T> inline T sqrtInverted(const T& a);

src/Math/Test/VectorTest.cpp

@@ -78,6 +78,7 @@ class VectorTest: public Corrade::TestSuite::Tester {
         void dot();
         void dotSelf();
         void length();
+        void lengthInverted();
         void normalized();
 
         void sum();
@@ -123,6 +124,7 @@ VectorTest::VectorTest() {
               &VectorTest::dot,
               &VectorTest::dotSelf,
               &VectorTest::length,
+              &VectorTest::lengthInverted,
               &VectorTest::normalized,
 
               &VectorTest::sum,
@@ -310,6 +312,10 @@ void VectorTest::length() {
     CORRADE_COMPARE(Vector4(1.0f, 2.0f, 3.0f, 4.0f).length(), 5.4772256f);
 }
 
+void VectorTest::lengthInverted() {
+    CORRADE_COMPARE(Vector4(1.0f, 2.0f, 3.0f, 4.0f).lengthInverted(), 0.182574f);
+}
+
 void VectorTest::normalized() {
     CORRADE_COMPARE(Vector4(1.0f, 1.0f, 1.0f, 1.0f).normalized(), Vector4(0.5f, 0.5f, 0.5f, 0.5f));
 }

src/Math/Vector.h

@@ -457,20 +457,32 @@ template<std::size_t size, class T> class Vector {
          * values. @f[
          *      |\boldsymbol a| = \sqrt{\boldsymbol a \cdot \boldsymbol a}
          * @f]
-         * @see Math::sqrt(), normalized()
+         * @see lengthInverted(), Math::sqrt(), normalized()
          * @todo something like std::hypot() for possibly better precision?
          */
         inline T length() const {
             return std::sqrt(dot());
         }
 
+        /**
+         * @brief Inverse vector length
+         *
+         * @f[
+         *      \frac{1}{|\boldsymbol a|} = \frac{1}{\sqrt{\boldsymbol a \cdot \boldsymbol a}}
+         * @f]
+         * @see length(), Math::sqrtInverted(), normalized()
+         */
+        inline T lengthInverted() const {
+            return T(1)/length();
+        }
+
         /**
          * @brief Normalized vector (of unit length)
          *
          * @see isNormalized()
          */
         inline Vector<size, T> normalized() const {
-            return *this/length();
+            return *this*lengthInverted();
         }
 
         /**