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/* ----------------------------------------------------------------------- *
 * This file is part of GEL, http://www.imm.dtu.dk/GEL
 * Copyright (C) the authors and DTU Informatics
 * For license and list of authors, see ../../doc/intro.pdf
 * ----------------------------------------------------------------------- */

/** @file ArithSqMat2x2Float.h
 * abstract 2x2 floating point matrix class
 */

#ifndef __CGLA_ARITHSQMAT2X2FLOAT_H__
#define __CGLA_ARITHSQMAT2X2FLOAT_H__

#include "ExceptionStandard.h"
#include "ArithSqMatFloat.h"


namespace CGLA 
{

  CGLA_DERIVEEXCEPTION(Mat2x2fException);

  /** \brief Two by two float matrix template. 

        This class template is useful for various vector transformations 
        in the plane. */
  template<class V, class M>
  class ArithSqMat2x2Float: public ArithSqMatFloat<V,M, 2>
  {
  public:

    /// Vector type
    typedef V VectorType;

    /// The type of a matrix element
    typedef typename V::ScalarType ScalarType;

  public:

    /// Construct a Mat2x2f from two Vec2f vectors.
    ArithSqMat2x2Float(V a, V b): 
      ArithSqMatFloat<V, M, 2> (a,b) {}

    /// Construct a Mat2x2f from four scalars.
    ArithSqMat2x2Float(ScalarType a, ScalarType b, 
                       ScalarType c, ScalarType d): 
      ArithSqMatFloat<V, M, 2>(V(a,b),V(c,d)) {}
  
    /// Construct the NAN matrix
    ArithSqMat2x2Float() {}

    /// Construct a matrix from a single scalar value.
    explicit ArithSqMat2x2Float(ScalarType a): 
      ArithSqMatFloat<V, M, 2>(a) {}
  };

  /** Compute the determinant of a Mat2x2f. This function is faster than
      the generic determinant function for ArithSqMat */
  template<class V, class M>
  inline typename ArithSqMat2x2Float<V,M>::ScalarType 
  determinant(const ArithSqMat2x2Float<V,M> & m)
  {
    return m[0][0]*m[1][1]-m[0][1]*m[1][0];
  }

  template<class V, class M>
  const M invert(const ArithSqMat2x2Float<V,M>& m)
  {
    typename M::ScalarType det = determinant(m);
    if( !is_tiny(fabs(det)))
      {
        return M(m[1][1]/det, -m[0][1]/det,-m[1][0]/det, m[0][0]/det);
      }
    throw Mat2x2fException("Cannot invert matrix");
  }


}
#endif