Changeset 1399 for trunk/yat

Timestamp:

Aug 7, 2008, 12:52:39 AM (15 years ago)

Author:

Peter

Message:

refs #369 added a function to create a boost::transform_iterator that was mentioned in ticket:369 - should probably add the corresponding for pair::second too.

File:

• trunk/yat/utility/stl_utility.h (modified) (2 diffs)

trunk/yat/utility/stl_utility.h

@@ -35 +35 @@
 /// extensions to STL functionality.
 ///
+
+#include <boost/iterator/transform_iterator.hpp>
+#include <boost/mpl/if.hpp>
+#include <boost/type_traits/is_const.hpp>
+#include <boost/type_traits/add_const.hpp>
 
 #include <algorithm>
@@ -266 +271 @@
   };
 
+  /**
+     \brief Functor that return std::pair.first
+
+     \see pair_first_iterator
+
+     \since New in yat 0.5
+   */
+  template <class Pair>
+  struct PairFirst 
+  {
+    /**
+       The type returned is Pair::first_type& with the exception when
+       Pair is const and Pair::first_type is non-const, in which case
+       const Pair::first_type& is return type.
+     */
+    typedef typename boost::mpl::if_<
+                  typename boost::is_const<Pair>::type, 
+                  typename boost::add_const<typename Pair::first_type>::type&,
+                  typename Pair::first_type&>::type result_type;
+    
+    /**
+       The argument type is Pair&.
+     */
+    typedef Pair& argument_type;
+
+    /**
+       \return p.first
+     */
+    inline result_type operator()(argument_type p) const
+    { return p.first; }
+
+  };
+
+
+  /**
+     Creates a transform_iterator that transforms an iterator with
+     value type std::pair to an iterator with value type
+     std::pair::first_type. This can be used, for example, to
+     communicate between a std::map and std::vector
+
+     \code
+     std::map<std::string, int> map;
+     ...
+     std::vector<std::string> vec;
+     vec.resize(map.size());
+     std::copy(pair_first_iterator(map.begin()), pair_first_iterator(map.end()),
+               vec.begin());
+     \endcode
+
+     \since New in yat 0.5
+   */
+  template<class Iter>
+  boost::transform_iterator<
+    PairFirst<typename std::iterator_traits<Iter>::value_type>, 
+    Iter> pair_first_iterator(Iter i)
+  {
+    typedef PairFirst<typename std::iterator_traits<Iter>::value_type> PF; 
+    return boost::transform_iterator<PF, Iter>(i, PF());
+  }
+
+
+
+
   ///
   /// @brief Function converting a string to lower case