Add an example showing how to use C++11 random distributions

Eigen/src/Core/CwiseNullaryOp.h

@@ -138,6 +138,9 @@ DenseBase<Derived>::NullaryExpr(Index rows, Index cols, const CustomNullaryOp& f
   *
   * The template parameter \a CustomNullaryOp is the type of the functor.
   *
+  * Here is an example with C++11 random generators: \include random_cpp11.cpp
+  * Output: \verbinclude random_cpp11.out
+  * 
   * \sa class CwiseNullaryOp
   */
 template<typename Derived>

Eigen/src/Core/Random.h

@@ -48,6 +48,8 @@ struct functor_traits<scalar_random_op<Scalar> >
   * a temporary matrix whenever it is nested in a larger expression. This prevents unexpected
   * behavior with expressions involving random matrices.
   * 
+  * See DenseBase::NullaryExpr(Index, const CustomNullaryOp&) for an example using C++11 random generators.
+  *
   * \sa DenseBase::setRandom(), DenseBase::Random(Index), DenseBase::Random()
   */
 template<typename Derived>

doc/special_examples/CMakeLists.txt

@@ -19,3 +19,22 @@ if(QT4_FOUND)
                      
   add_dependencies(all_examples Tutorial_sparse_example)
 endif(QT4_FOUND)
+
+check_cxx_compiler_flag("-std=c++11" EIGEN_COMPILER_SUPPORT_CPP11)
+if(EIGEN_COMPILER_SUPPORT_CPP11)
+  add_executable(random_cpp11 random_cpp11.cpp)
+  target_link_libraries(random_cpp11 ${EIGEN_STANDARD_LIBRARIES_TO_LINK_TO})
+  add_dependencies(all_examples random_cpp11)
+  ei_add_target_property(random_cpp11 COMPILE_FLAGS "-std=c++11")
+  
+  get_target_property(random_cpp11_exec
+                      random_cpp11 LOCATION)
+  add_custom_command(
+    TARGET random_cpp11
+    POST_BUILD
+    COMMAND ${random_cpp11_exec}
+    ARGS >${CMAKE_CURRENT_BINARY_DIR}/random_cpp11.out
+  )
+  
+  
+endif()

doc/special_examples/random_cpp11.cpp

@@ -0,0 +1,14 @@
+#include <Eigen/Core>
+#include <iostream>
+#include <random>
+
+using namespace Eigen;
+
+int main() {
+  std::default_random_engine generator;
+  std::poisson_distribution<int> distribution(4.1);
+  auto poisson = [&] (int) {return distribution(generator);};
+
+  RowVectorXi v = RowVectorXi::NullaryExpr(10, poisson );
+  std::cout << v << "\n";
+}