filter_iterator

[SVN r850]

include/boost/iterator/iterator_adaptors.hpp

@@ -693,6 +693,12 @@ namespace boost {
     }
   };
 
+  template <class BidirectionalIterator>
+  reverse_iterator<BidirectionalIterator> make_reverse_iterator(BidirectionalIterator x)
+  {
+      return reverse_iterator<BidirectionalIterator>(x);
+  }
+
   //
   // TODO fix category
   //
@@ -734,6 +740,8 @@ namespace boost {
   private:
     typename super_t::value_type dereference() const { return m_f(super_t::dereference()); }
 
+    // Probably should be the initial base class so it can be
+    // optimized away via EBO if it is an empty class.
     AdaptableUnaryFunction m_f;
   };
 
@@ -744,7 +752,7 @@ namespace boost {
     //
     // Detection for whether a type has a nested `element_type'
     // typedef. Used to detect smart pointers. For compilers not
-    // supporting mpl's has_xxx, we supply specialzations. However, we
+    // supporting mpl's has_xxx, we supply specializations. However, we
     // really ought to have a specializable is_pointer template which
     // can be used instead with something like
     // boost/python/pointee.hpp to find the value_type.
@@ -849,9 +857,9 @@ namespace boost {
         , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0
 # endif 
         )
-        
-      : super_t(y.base())  {}
-
+      : super_t(y.base())
+      {}
+      
   private:    
     typename super_t::reference dereference() const { return **this->base(); }
 
@@ -871,6 +879,90 @@ namespace boost {
     return indirect_iterator<Iter, Traits>(x);
   }
 
+  template <class Iterator>
+  struct filter_iterator_traits
+      : detail::iterator_traits<Iterator>
+  {
+      typedef iterator_tag<
+            typename return_category<Iterator>::type
+          , forward_traversal_tag
+      > iterator_category;
+  };
+
+  template <class Predicate, class Iterator>
+  class filter_iterator
+      : public iterator_adaptor<
+           filter_iterator<Predicate, Iterator>, Iterator,
+           typename filter_iterator_traits<Iterator>::value_type,
+           typename filter_iterator_traits<Iterator>::reference,
+           typename filter_iterator_traits<Iterator>::pointer,
+           typename filter_iterator_traits<Iterator>::iterator_category,
+           typename filter_iterator_traits<Iterator>::difference_type
+        >
+  {
+      typedef iterator_adaptor<
+           filter_iterator<Predicate, Iterator>, Iterator,
+           typename filter_iterator_traits<Iterator>::value_type,
+           typename filter_iterator_traits<Iterator>::reference,
+           typename filter_iterator_traits<Iterator>::pointer,
+           typename filter_iterator_traits<Iterator>::iterator_category,
+           typename filter_iterator_traits<Iterator>::difference_type > super_t;
+
+      friend class iterator_core_access;
+
+   public:
+      filter_iterator() { }
+
+      filter_iterator(Predicate f, Iterator x, Iterator end = Iterator())
+          : super_t(x), m_predicate(f), m_end(end)
+      {
+          satisfy_predicate();
+      }
+
+      filter_iterator(Iterator x, Iterator end = Iterator())
+          : super_t(x), m_predicate(), m_end(end)
+      {
+          satisfy_predicate();
+      }
+
+      template<class OtherIterator>
+      filter_iterator(
+          filter_iterator<Predicate, OtherIterator> const& t
+  # ifndef BOOST_NO_ENABLE_IF_CONSTRUCTORS
+          , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0
+  # endif 
+          )
+          : super_t(t.base()), m_predicate(t.predicate()), m_end(t.end()) {}
+
+      Predicate predicate() const { return m_predicate; }
+
+      Iterator end() const { return m_end; }
+
+   private:
+      void increment()
+      {
+          super_t::increment();
+          satisfy_predicate();
+      }
+
+      void satisfy_predicate()
+      {
+          while (this->base() != this->m_end && !this->m_predicate(*this->base()))
+              super_t::increment();
+      }
+
+      // Probably should be the initial base class so it can be
+      // optimized away via EBO if it is an empty class.
+      Predicate m_predicate;
+      Iterator m_end;
+  };
+
+  template <class Predicate, class Iterator>
+  filter_iterator<Predicate,Iterator>
+  make_filter_iterator(Predicate f, Iterator x, Iterator end = Iterator())
+  {
+      return filter_iterator<Predicate,Iterator>(f,x,end);
+  }
 } // namespace boost
 
 //

test/Jamfile

@@ -4,5 +4,6 @@ run concept_tests.cpp ;
 run iterator_adaptor_cc.cpp ;
 run transform_iterator_test.cpp ;
 run indirect_iterator_test.cpp ;
+run filter_iterator_test.cpp ;
 compile-fail interoperable_fail.cpp ;
 compile-fail is_convertible_fail.cpp ;

test/filter_iterator_test.cpp

@@ -0,0 +1,81 @@
+// Copyright David Abrahams 2003. Permission to copy, use,
+// modify, sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+
+#include <boost/iterator/iterator_adaptors.hpp>
+#include <boost/iterator/new_iterator_tests.hpp>
+
+#include <deque>
+#include <iostream>
+
+using boost::dummyT;
+
+struct one_or_four {
+  bool operator()(dummyT x) const {
+    return x.foo() == 1 || x.foo() == 4;
+  }
+};
+
+#ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
+namespace boost { namespace detail
+{
+  template<> struct iterator_traits<dummyT*>
+  : ptr_iter_traits<dummyT> {};
+}}
+#endif
+
+
+// Test filter iterator
+int main()
+{
+    dummyT array[] = { dummyT(0), dummyT(1), dummyT(2), 
+                       dummyT(3), dummyT(4), dummyT(5) };
+    const int N = sizeof(array)/sizeof(dummyT);
+
+    typedef boost::filter_iterator<one_or_four, dummyT*> filter_iter;
+
+    boost::forward_iterator_test(
+        filter_iter(one_or_four(), array, array+N)
+        , dummyT(1), dummyT(4));
+
+# if 0
+    BOOST_STATIC_ASSERT(
+        (!boost::detail::is_bidirectional_traversal_iterator<
+            boost::traversal_category<filter_iter>::type
+          >::value) );
+# endif
+    
+    // On compilers not supporting partial specialization, we can do more type
+    // deduction with deque iterators than with pointers... unless the library
+    // is broken ;-(
+    std::deque<dummyT> array2;
+    std::copy(array+0, array+N, std::back_inserter(array2));
+    boost::forward_iterator_test(
+        boost::make_filter_iterator(one_or_four(), array2.begin(), array2.end()),
+        dummyT(1), dummyT(4));
+
+    boost::forward_iterator_test(
+        boost::make_filter_iterator(one_or_four(), array2.begin(), array2.end()),
+        dummyT(1), dummyT(4));
+
+    boost::forward_iterator_test(
+        boost::make_filter_iterator(
+              one_or_four()
+            , boost::make_reverse_iterator(array2.end())
+            , boost::make_reverse_iterator(array2.begin())
+            ),
+        dummyT(4), dummyT(1));
+    
+    boost::forward_iterator_test(
+        filter_iter(array+0, array+N),
+        dummyT(1), dummyT(4));
+
+    boost::forward_iterator_test(
+        filter_iter(one_or_four(), array, array + N),
+        dummyT(1), dummyT(4));
+
+  std::cout << "test successful " << std::endl;
+  return 0;
+}