change the Arch constants: const int ---> enum, more explicit names, and use

of a namespace instead of Prefix_Name.

Eigen/src/Core/util/Constants.h

@@ -228,8 +228,7 @@ enum {
   RowMajor = 0x1,  // it is only a coincidence that this is equal to RowMajorBit -- don't rely on that
   /** \internal Align the matrix itself if it is vectorizable fixed-size */
   AutoAlign = 0,
-  /** \internal Don't require alignment for the matrix itself (the array of coefficients, if dynamically allocated, may still be
-                requested to be aligned) */
+  /** \internal Don't require alignment for the matrix itself (the array of coefficients, if dynamically allocated, may still be requested to be aligned) */ // FIXME --- clarify the situation
   DontAlign = 0x2
 };
 
@@ -277,16 +276,20 @@ enum TransformTraits {
   Projective    = 0x20
 };
 
-const int EiArch_Generic = 0x0;
-const int EiArch_SSE     = 0x1;
-const int EiArch_AltiVec = 0x2;
-
+namespace Architecture
+{
+  enum Type {
+    Generic = 0x0,
+    SSE = 0x1,
+    AltiVec = 0x2,
 #if defined EIGEN_VECTORIZE_SSE
-  const int EiArch = EiArch_SSE;
+    Target = SSE
 #elif defined EIGEN_VECTORIZE_ALTIVEC
-  const int EiArch = EiArch_AltiVec;
+    Target = AltiVec
 #else
-  const int EiArch = EiArch_Generic;
+    Target = Generic
 #endif
+  };
+}
 
 #endif // EIGEN_CONSTANTS_H

Eigen/src/Geometry/OrthoMethods.h

@@ -90,8 +90,9 @@ MatrixBase<Derived>::cross3(const MatrixBase<OtherDerived>& other) const
   const DerivedNested lhs(derived());
   const OtherDerivedNested rhs(other.derived());
 
-  return ei_cross3_impl<EiArch,typename ei_cleantype<DerivedNested>::type,
-                               typename ei_cleantype<OtherDerivedNested>::type>::run(lhs,rhs);
+  return ei_cross3_impl<Architecture::Target,
+                        typename ei_cleantype<DerivedNested>::type,
+                        typename ei_cleantype<OtherDerivedNested>::type>::run(lhs,rhs);
 }
 
 /** \returns a matrix expression of the cross product of each column or row

Eigen/src/Geometry/Quaternion.h

@@ -367,7 +367,7 @@ QuaternionBase<Derived>::operator* (const QuaternionBase<OtherDerived>& other) c
 {
   EIGEN_STATIC_ASSERT((ei_is_same_type<typename Derived::Scalar, typename OtherDerived::Scalar>::ret),
    YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
-  return ei_quat_product<EiArch, Derived, OtherDerived,
+  return ei_quat_product<Architecture::Target, Derived, OtherDerived,
                          typename ei_traits<Derived>::Scalar,
                          ei_traits<Derived>::PacketAccess && ei_traits<OtherDerived>::PacketAccess>::run(*this, other);
 }

Eigen/src/Geometry/arch/Geometry_SSE.h

@@ -26,7 +26,8 @@
 #ifndef EIGEN_GEOMETRY_SSE_H
 #define EIGEN_GEOMETRY_SSE_H
 
-template<class Derived, class OtherDerived> struct ei_quat_product<EiArch_SSE, Derived, OtherDerived, float, Aligned>
+template<class Derived, class OtherDerived>
+struct ei_quat_product<Architecture::SSE, Derived, OtherDerived, float, Aligned>
 {
   inline static Quaternion<float> run(const QuaternionBase<Derived>& _a, const QuaternionBase<OtherDerived>& _b)
   {
@@ -48,7 +49,8 @@ template<class Derived, class OtherDerived> struct ei_quat_product<EiArch_SSE, D
 };
 
 template<typename VectorLhs,typename VectorRhs>
-struct ei_cross3_impl<EiArch_SSE,VectorLhs,VectorRhs,float,true> {
+struct ei_cross3_impl<Architecture::SSE,VectorLhs,VectorRhs,float,true>
+{
   inline static typename ei_plain_matrix_type<VectorLhs>::type
   run(const VectorLhs& lhs, const VectorRhs& rhs)
   {