+
+struct firster {
+ template <class P1, class P2>
+ P1 operator()(std::pair<P1, P2> const & p) {
+ return p.first;
+ }
+};
+
+
+/**
+ * copy elements in the given range to the output iterator
+ * if the predicate evaluates as true
+ */
+template <class InputIter, class OutputIter, class Func>
+OutputIter copy_if(InputIter first, InputIter last,
+ OutputIter result, Func func)
+{
+ for (; first != last; ++first) {
+ if (func(*first)) {
+ *result++ = *first;
+ }
+ }
+ return result;
+}
+
+
+/// A slot in replacement for std::count for systems where it is broken.
+template <class Iterator, class T>
+typename std::iterator_traits<Iterator>::difference_type
+count (Iterator first, Iterator last, T const & value)
+{
+#ifdef HAVE_STD_COUNT
+ return std::count(first, last, value);
+#else
+ std::iterator_traits<Iterator>::difference_type n = 0;
+ while (first != last)
+ if (*first++ == value) ++n;
+ return n;