add fromArray() and wrapArray().

For example, the following now works:

  double a1[3] = {1.0, 3.0, 2.0}, a2[3];
  Vector3d::wrapArray(a2) = 2 * Vector3d::fromArray(a1);
  cout << Vector3d::fromArray(a2) << endl; // output: 2,6,4

doc/tutorial.cpp

@@ -32,5 +32,10 @@ int main(int, char **)
   cout << "Column 1 of m2 is:" << endl << m2.col(1) << endl;
   cout << "The transpose of m2 is:" << endl << m2.transpose() << endl;
   cout << "The matrix m2 with row 0 and column 1 removed is:" << endl << m2.minor(0,1) << endl;
+  
+  double a1[3] = {1.0, 3.0, 2.0};
+  double a2[3];
+  Vector3d::wrapArray(a2) = 2 * Vector3d::fromArray(a1);
+  cout << Vector3d::fromArray(a2) << endl;
   return 0;
 }

src/Core.h

@@ -1,4 +1,3 @@
-
 #include <iostream>
 #include <complex>
 #include <cassert>
@@ -30,5 +29,7 @@ namespace Eigen {
 #include "Core/Zero.h"
 #include "Core/Identity.h"
 #include "Core/Fuzzy.h"
+#include "Core/FromArray.h"
+#include "Core/WrapArray.h"
 
 } // namespace Eigen

src/Core/FromArray.h

@@ -0,0 +1,66 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra. Eigen itself is part of the KDE project.
+//
+// Copyright (C) 2006-2007 Benoit Jacob <jacob@math.jussieu.fr>
+//
+// Eigen is free software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation; either version 2 or (at your option) any later version.
+//
+// Eigen is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+// details.
+//
+// You should have received a copy of the GNU General Public License along
+// with Eigen; if not, write to the Free Software Foundation, Inc., 51
+// Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+// As a special exception, if other files instantiate templates or use macros
+// or functions from this file, or you compile this file and link it
+// with other works to produce a work based on this file, this file does not
+// by itself cause the resulting work to be covered by the GNU General Public
+// License. This exception does not invalidate any other reasons why a work
+// based on this file might be covered by the GNU General Public License.
+
+#ifndef EI_FROMARRAY_H
+#define EI_FROMARRAY_H
+
+template<typename MatrixType> class FromArray
+  : public Object<typename MatrixType::Scalar, FromArray<MatrixType> >
+{
+  public:
+    typedef typename MatrixType::Scalar Scalar;
+    friend class Object<Scalar, FromArray<MatrixType> >;
+    
+    static const int RowsAtCompileTime = MatrixType::RowsAtCompileTime,
+                     ColsAtCompileTime = MatrixType::ColsAtCompileTime;
+
+    FromArray(int rows, int cols, const Scalar* array) : m_rows(rows), m_cols(cols), m_array(array)
+    {
+      assert(rows > 0 && cols > 0);
+    }
+    
+  private:
+    FromArray& _ref() { return *this; }
+    const FromArray& _constRef() const { return *this; }
+    int _rows() const { return m_rows; }
+    int _cols() const { return m_cols; }
+    
+    const Scalar& _read(int row, int col) const
+    {
+      return m_array[row + col * m_rows];
+    }
+    
+  protected:
+    int m_rows, m_cols;
+    const Scalar* m_array;
+};
+
+template<typename Scalar, typename Derived>
+FromArray<Derived> Object<Scalar, Derived>::fromArray(const Scalar* array, int rows, int cols)
+{
+  return FromArray<Derived>(rows, cols, array);
+}
+
+#endif // EI_FROMARRAY_H

src/Core/Object.h

@@ -117,6 +117,10 @@ template<typename Scalar, typename Derived> class Object
     zero(int rows = RowsAtCompileTime, int cols = ColsAtCompileTime);
     static Identity<Derived>
     identity(int rows = RowsAtCompileTime);
+    static FromArray<Derived>
+    fromArray(const Scalar* array, int rows = RowsAtCompileTime, int cols = ColsAtCompileTime);
+    static WrapArray<Derived>
+    wrapArray(Scalar* array, int rows = RowsAtCompileTime, int cols = ColsAtCompileTime);
     
     template<typename OtherDerived>
     bool isApprox(

src/Core/Util.h

@@ -59,6 +59,8 @@ template<typename MatrixType> class Random;
 template<typename MatrixType> class Zero;
 template<typename MatrixType> class Identity;
 template<typename ExpressionType> class Eval;
+template<typename MatrixType> class FromArray;
+template<typename MatrixType> class WrapArray;
 
 template<typename T> struct ForwardDecl
 {

src/Core/WrapArray.h

@@ -0,0 +1,73 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra. Eigen itself is part of the KDE project.
+//
+// Copyright (C) 2006-2007 Benoit Jacob <jacob@math.jussieu.fr>
+//
+// Eigen is free software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the Free Software
+// Foundation; either version 2 or (at your option) any later version.
+//
+// Eigen is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+// details.
+//
+// You should have received a copy of the GNU General Public License along
+// with Eigen; if not, write to the Free Software Foundation, Inc., 51
+// Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+// As a special exception, if other files instantiate templates or use macros
+// or functions from this file, or you compile this file and link it
+// with other works to produce a work based on this file, this file does not
+// by itself cause the resulting work to be covered by the GNU General Public
+// License. This exception does not invalidate any other reasons why a work
+// based on this file might be covered by the GNU General Public License.
+
+#ifndef EI_WRAPARRAY_H
+#define EI_WRAPARRAY_H
+
+template<typename MatrixType> class WrapArray
+  : public Object<typename MatrixType::Scalar, WrapArray<MatrixType> >
+{
+  public:
+    typedef typename MatrixType::Scalar Scalar;
+    friend class Object<Scalar, WrapArray<MatrixType> >;
+    
+    static const int RowsAtCompileTime = MatrixType::RowsAtCompileTime,
+                     ColsAtCompileTime = MatrixType::ColsAtCompileTime;
+
+    WrapArray(int rows, int cols, Scalar* array) : m_rows(rows), m_cols(cols), m_array(array)
+    {
+      assert(rows > 0 && cols > 0);
+    }
+    
+    EI_INHERIT_ASSIGNMENT_OPERATORS(WrapArray)
+    
+  private:
+    WrapArray& _ref() { return *this; }
+    const WrapArray& _constRef() const { return *this; }
+    int _rows() const { return m_rows; }
+    int _cols() const { return m_cols; }
+    
+    const Scalar& _read(int row, int col) const
+    {
+      return m_array[row + col * m_rows];
+    }
+    
+    Scalar& _write(int row, int col) const
+    {
+      return m_array[row + col * m_rows];
+    }
+    
+  protected:
+    int m_rows, m_cols;
+    Scalar* m_array;
+};
+
+template<typename Scalar, typename Derived>
+WrapArray<Derived> Object<Scalar, Derived>::wrapArray(Scalar* array, int rows, int cols)
+{
+  return WrapArray<Derived>(rows, cols, array);
+}
+
+#endif // EI_WRAPARRAY_H