text: ///////////////////////////////////////////////////////////////////////////////////
  /// OpenGL Mathematics (glm.g-truc.net)
  ///
  /// Copyright (c) 2005 - 2015 G-Truc Creation (www.g-truc.net)
  /// Permission is hereby granted, free of charge, to any person obtaining a copy
  /// of this software and associated documentation files (the "Software"), to deal
  /// in the Software without restriction, including without limitation the rights
  /// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  /// copies of the Software, and to permit persons to whom the Software is
  /// furnished to do so, subject to the following conditions:
  /// 
  /// The above copyright notice and this permission notice shall be included in
  /// all copies or substantial portions of the Software.
  /// 
  /// Restrictions:
  ///        By making use of the Software for military purposes, you choose to make
  ///        a Bunny unhappy.
  /// 
  /// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  /// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  /// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  /// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  /// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  /// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  /// THE SOFTWARE.
  ///
  /// @ref gtx_fast_square_root
  /// @file glm/gtx/fast_square_root.hpp
  /// @date 2006-01-04 / 2011-06-07
  /// @author Christophe Riccio
  ///
  /// @see core (dependence)
  ///
  /// @defgroup gtx_fast_square_root GLM_GTX_fast_square_root
  /// @ingroup gtx
  /// 
  /// @brief Fast but less accurate implementations of square root based functions.
  /// - Sqrt optimisation based on Newton's method, 
  /// www.gamedev.net/community/forums/topic.asp?topic id=139956
  /// 
  /// <glm/gtx/fast_square_root.hpp> need to be included to use these functionalities.
  ///////////////////////////////////////////////////////////////////////////////////
  
  #pragma once
  
  // Dependency:
  #include "../common.hpp"
  #include "../exponential.hpp"
  #include "../geometric.hpp"
  
  #if (defined(GLM_MESSAGES) && !defined(GLM_EXT_INCLUDED))
  #    pragma message("GLM: GLM_GTX_fast_square_root extension included")
  #endif
  
  namespace glm
  {
      /// @addtogroup gtx_fast_square_root
      /// @{
  
      /// Faster than the common sqrt function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename genType> 
      GLM_FUNC_DECL genType fastSqrt(genType x);
  
      /// Faster than the common sqrt function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename T, precision P, template <typename, precision> class vecType>
      GLM_FUNC_DECL vecType<T, P> fastSqrt(vecType<T, P> const & x);
  
      /// Faster than the common inversesqrt function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename genType> 
      GLM_FUNC_DECL genType fastInverseSqrt(genType x);
  
      /// Faster than the common inversesqrt function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename T, precision P, template <typename, precision> class vecType>
      GLM_FUNC_DECL vecType<T, P> fastInverseSqrt(vecType<T, P> const & x);
  
      /// Faster than the common length function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename genType>
      GLM_FUNC_DECL genType fastLength(genType x);
  
      /// Faster than the common length function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename T, precision P, template <typename, precision> class vecType>
      GLM_FUNC_DECL T fastLength(vecType<T, P> const & x);
  
      /// Faster than the common distance function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename genType>
      GLM_FUNC_DECL genType fastDistance(genType x, genType y);
  
      /// Faster than the common distance function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename T, precision P, template <typename, precision> class vecType>
      GLM_FUNC_DECL T fastDistance(vecType<T, P> const & x, vecType<T, P> const & y);
  
      /// Faster than the common normalize function but less accurate.
      ///
      /// @see gtx_fast_square_root extension.
      template <typename genType> 
      GLM_FUNC_DECL genType fastNormalize(genType const & x);
  
      /// @}
  }// namespace glm
  
  #include "fast_square_root.inl"
  