PR 572: Add initializer list constructors to Matrix and Array (include unit tests and doc)

- {1,2,3,4,5,...} for fixed-size vectors only
- {{1,2,3},{4,5,6}} for the general cases
- {{1,2,3,4,5,....}} is allowed for both row and column-vector

Eigen/src/Core/Matrix.h

@@ -301,6 +301,20 @@ class Matrix
       Base::_check_template_params();
       Base::template _init2<T0,T1>(x, y);
     }
+
+    #if EIGEN_HAS_CXX11
+    template<typename T>
+    EIGEN_DEVICE_FUNC
+    explicit EIGEN_STRONG_INLINE Matrix(const std::initializer_list<T>& list,
+      typename internal::enable_if<internal::is_same<T, Scalar>::value, T>::type* = 0,
+      typename internal::enable_if<RowsAtCompileTime != Dynamic
+                                   && ColsAtCompileTime != Dynamic
+                                   && IsVectorAtCompileTime == 1, T>::type* = 0) : Base(list) {}
+
+    EIGEN_DEVICE_FUNC
+    explicit EIGEN_STRONG_INLINE Matrix(const std::initializer_list<std::initializer_list<Scalar>>& list) : Base(list) {}
+    #endif // end EIGEN_HAS_CXX11
+
     #else
     /** \brief Constructs a fixed-sized matrix initialized with coefficients starting at \a data */
     EIGEN_DEVICE_FUNC
@@ -338,7 +352,41 @@ class Matrix
     
     /** \brief Constructs an initialized 2D vector with given coefficients */
     Matrix(const Scalar& x, const Scalar& y);
-    #endif
+
+    /** \copydoc PlainObjectBase::PlainObjectBase(const std::initializer_list<Scalar>& list)
+     *
+     * Example: \include Matrix_initializer_list2_cxx11.cpp
+     * Output: \verbinclude Matrix_initializer_list2_cxx11.out
+     *
+     * \sa Matrix::Matrix(const Scalar& x, const Scalar& y, const Scalar& z)
+     * \sa Matrix::Matrix(const Scalar& x, const Scalar& y, const Scalar& z, const Scalar& w) */
+    EIGEN_DEVICE_FUNC
+    explicit EIGEN_STRONG_INLINE Matrix(const std::initializer_list<Scalar>& list);
+
+    /**
+     * \brief Constructs a matrix and initializes it by elements given by an initializer list of initializer lists \cpp11
+     * 
+     * This constructor distinguishes between the construction of arbitrary matrices and matrices with one fixed dimension,
+     * i.e., vectors or rowvectors.
+     * 
+     * In the general case, the constructor takes an initializer list, representing the matrix rows, that contains for
+     * each row an initializer list, representing a single column, containing scalar values. Each of the inner
+     * initializer lists must contain the same number of elements. 
+     * 
+     * In the case of matrices with one fixed dimension, an initializer list containing just one other initializer list
+     * that contains the matrix elements can be passed. Therefore \c VectorXi\c {{1,\c 2,\c 3,\c 4}} is legal and the more
+     * verbose syntax \c VectorXi\c {{1},\c {2},\c {3},\c {4}} can be avoided.
+     * 
+     * \warning In the case of fixed-sized matrices, the initializer list size must be equal to the matrix \a rows rows
+     * and \a cols columns.
+     *  
+     * Example: \include Matrix_initializer_list_cxx11.cpp
+     * Output: \verbinclude Matrix_initializer_list_cxx11.out
+     */
+    EIGEN_DEVICE_FUNC
+    explicit EIGEN_STRONG_INLINE Matrix(const std::initializer_list<std::initializer_list<Scalar>>& list);
+
+    #endif  // end EIGEN_PARSED_BY_DOXYGEN
 
     /** \brief Constructs an initialized 3D vector with given coefficients */
     EIGEN_DEVICE_FUNC