Add Matrix::resizeLike(other) convenience function and test.

Eigen/src/Core/Matrix.h

@@ -248,6 +248,29 @@ class Matrix
         m_storage.resize(size, size, 1);
     }
 
+    /** Resizes *this to have the same dimensions as \a other.
+      * Takes care of doing all the checking that's needed.
+      *
+      * Note that copying a row-vector into a vector (and conversely) is allowed.
+      * The resizing, if any, is then done in the appropriate way so that row-vectors
+      * remain row-vectors and vectors remain vectors.
+      */
+    template<typename OtherDerived>
+    EIGEN_STRONG_INLINE void resizeLike(const MatrixBase<OtherDerived>& other)
+    {
+      if(RowsAtCompileTime == 1)
+      {
+        ei_assert(other.isVector());
+        resize(1, other.size());
+      }
+      else if(ColsAtCompileTime == 1)
+      {
+        ei_assert(other.isVector());
+        resize(other.size(), 1);
+      }
+      else resize(other.rows(), other.cols());
+    }
+
     /** Copies the value of the expression \a other into \c *this with automatic resizing.
       *
       * *this might be resized to match the dimensions of \a other. If *this was a null matrix (not already initialized),
@@ -468,18 +491,7 @@ class Matrix
                  : (rows() == other.rows() && cols() == other.cols())))
         && "Size mismatch. Automatic resizing is disabled because EIGEN_NO_AUTOMATIC_RESIZING is defined");
       #endif
-
+      resizeLike(other);
-      if(RowsAtCompileTime == 1)
-      {
-        ei_assert(other.isVector());
-        resize(1, other.size());
-      }
-      else if(ColsAtCompileTime == 1)
-      {
-        ei_assert(other.isVector());
-        resize(other.size(), 1);
-      }
-      else resize(other.rows(), other.cols());
     }
 
     /** \internal Copies the value of the expression \a other into \c *this with automatic resizing.

test/CMakeLists.txt

@@ -211,6 +211,7 @@ ei_add_test(parametrizedline)
 ei_add_test(alignedbox)
 ei_add_test(regression)
 ei_add_test(stdvector)
+ei_add_test(resize)
 if(QT4_FOUND)
   ei_add_test(qtvector " " ${QT_QTCORE_LIBRARY})
 endif(QT4_FOUND)

test/resize.cpp

@@ -0,0 +1,56 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra. Eigen itself is part of the KDE project.
+//
+// Copyright (C) 2009 Keir Mierle <mierle@gmail.com>
+//
+// Eigen is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 3 of the License, or (at your option) any later version.
+//
+// Alternatively, 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 of
+// the License, 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 Lesser General Public License or the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License and a copy of the GNU General Public License along with
+// Eigen. If not, see <http://www.gnu.org/licenses/>.
+
+#include "main.h"
+
+template<int rows, int cols>
+void resizeLikeTest()
+{
+  MatrixXf A(rows, cols);
+  MatrixXf B;
+  Matrix<double, rows, cols> C;
+  B.resizeLike(A);
+  C.resizeLike(B);  // Shouldn't crash.
+  VERIFY(B.rows() == rows && B.cols() == cols);
+
+  VectorXf x(rows);
+  RowVectorXf y;
+  y.resizeLike(x);
+  VERIFY(y.rows() == 1 && y.cols() == rows);
+
+  y.resize(cols);
+  x.resizeLike(y);
+  VERIFY(x.rows() == cols && x.cols() == 1);
+}
+
+void resizeLikeTest12() { resizeLikeTest<1,2>(); }
+void resizeLikeTest1020() { resizeLikeTest<10,20>(); }
+void resizeLikeTest31() { resizeLikeTest<3,1>(); }
+
+void test_resize()
+{
+  CALL_SUBTEST( resizeLikeTest12() );
+  CALL_SUBTEST( resizeLikeTest1020() );
+  CALL_SUBTEST( resizeLikeTest31() );
+}