Added function_input_iterator from Dean Michael Berris; fixes #2893

[SVN r62615]

include/boost/iterator/function_input_iterator.hpp

@@ -0,0 +1,64 @@
+// Copyright 2009 (C) Dean Michael Berris <me@deanberris.com>
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef BOOST_FUNCTION_INPUT_ITERATOR
+#define BOOST_FUNCTION_INPUT_ITERATOR
+
+#include <boost/iterator/iterator_facade.hpp>
+
+namespace boost {
+
+    template <class Function, class Input>
+        class function_input_iterator
+        : public iterator_facade<
+            function_input_iterator<Function, Input>,
+            typename Function::result_type,
+            single_pass_traversal_tag,
+            typename Function::result_type const &
+            >
+    {
+        public:
+            function_input_iterator() {}
+            function_input_iterator(Function * f_, Input state_ = Input()) 
+                : f(f_), state(state_), value((*f)()) {}
+
+            void increment() {
+                value = (*f)();
+                ++state;
+            }
+
+            typename Function::result_type const & 
+            dereference() const {
+                return value;
+            }
+
+            bool equal(function_input_iterator const & other) const {
+                return f == other.f && state == other.state;
+            }
+
+        private:
+            Function * f;
+            Input state;
+            typename Function::result_type value;
+    };
+
+    template <class Function, class Input>
+    inline function_input_iterator<Function, Input>
+    make_function_input_iterator(Function & f, Input state) {
+        typedef function_input_iterator<Function, Input> result_t;
+        return result_t(&f, state);
+    }
+
+    struct infinite {
+        infinite & operator++() { return *this; }
+        infinite & operator++(int) { return *this; }
+        bool operator==(infinite &) const { return false; };
+        bool operator==(infinite const &) const { return false; };
+    };
+}
+
+#endif
+