Add util::algorithm::counter

Signed-off-by: janus_wel <janus.wel.3@gmail.com>

header/algorithm.hpp

@@ -23,6 +23,28 @@ namespace util {
             void operator()(T* p) { delete p; }
         };
 
+        // for std::generate() and std::generate_n()
+        template<typename T> class counter {
+            public:
+                typedef T   count_type;
+
+            private:
+                count_type first, returned;
+                const count_type increment;
+
+            public:
+                counter(count_type first, count_type increment)
+                    : first(first), increment(increment) {}
+                count_type operator()(void) {
+                    returned = first;
+                    first += increment;
+                    return returned;
+                }
+
+            private:
+                counter& operator=(const counter& rhs);
+        };
+
         // copy_if
         template<   typename InputIterator, typename OstreamIterator,
                     typename Predicate>

sample/algorithm/main.cpp

@@ -112,6 +112,16 @@ int main(const int argc, const char* const argv[]) {
 
     std::cerr << std::endl;
 
+    // counter
+    // from 0, increment 1
+    std::generate_n(
+            std::ostream_iterator<unsigned int>(std::cout, "\n"), 10,
+            util::algorithm::counter<unsigned int>(0, 1));
+    // from 0.1, increment 0.3
+    std::generate_n(
+            std::ostream_iterator<double>(std::cout, "\n"), 10,
+            util::algorithm::counter<double>(0.1, 0.3));
+
     return 0;
 }