bug #1286: automatically detect the available prototypes of functors passed to CwiseNullaryExpr such that functors have only to implement the operators that matters among:

 operator()()
 operator()(i)
 operator()(i,j)
Linear access is also automatically detected based on the availability of operator()(i,j).

1 files changed, 43 insertions, 0 deletions

diff --git a/Eigen/src/Core/util/Meta.h b/Eigen/src/Core/util/Meta.h
index b9beb6eb7..e69c78db2 100755
--- a/Eigen/src/Core/util/Meta.h
+++ b/Eigen/src/Core/util/Meta.h
@@ -22,6 +22,16 @@
 
 namespace Eigen {
 
+typedef EIGEN_DEFAULT_DENSE_INDEX_TYPE DenseIndex;
+
+/**
+ * \brief The Index type as used for the API.
+ * \details To change this, \c \#define the preprocessor symbol \c EIGEN_DEFAULT_DENSE_INDEX_TYPE.
+ * \sa \blank \ref TopicPreprocessorDirectives, StorageIndex.
+ */
+
+typedef EIGEN_DEFAULT_DENSE_INDEX_TYPE Index;
+
 namespace internal {
 
 /** \internal
@@ -371,6 +381,39 @@ struct has_ReturnType
   enum { value = sizeof(testFunctor<T>(0)) == sizeof(yes) };
 };
 
+template<int> struct any_int {};
+template<typename T> const T& return_ref();
+
+struct meta_yes { char data[1]; };
+struct meta_no  { char data[2]; };
+
+template <typename T>
+struct has_nullary_operator
+{
+  template <typename C> static meta_yes testFunctor(C const *,any_int< sizeof(return_ref<C>()()) > * = 0);
+  static meta_no testFunctor(...);
+
+  enum { value = sizeof(testFunctor(static_cast<T*>(0))) == sizeof(meta_yes) };
+};
+
+template <typename T>
+struct has_unary_operator
+{
+  template <typename C> static meta_yes testFunctor(C const *,any_int< sizeof(return_ref<C>()(Index(0))) > * = 0);
+  static meta_no testFunctor(...);
+
+  enum { value = sizeof(testFunctor(static_cast<T*>(0))) == sizeof(meta_yes) };
+};
+
+template <typename T>
+struct has_binary_operator
+{
+  template <typename C> static meta_yes testFunctor(C const *,any_int< sizeof(return_ref<C>()(Index(0),Index(0))) > * = 0);
+  static meta_no testFunctor(...);
+
+  enum { value = sizeof(testFunctor(static_cast<T*>(0))) == sizeof(meta_yes) };
+};
+
 /** \internal In short, it computes int(sqrt(\a Y)) with \a Y an integer.
   * Usage example: \code meta_sqrt<1023>::ret \endcode
   */