Added enumerate source

Author: jay-tux

inc/sources.hpp

@@ -21,7 +21,7 @@ namespace fpgen {
  *  \tparam Container The container type.
  *  \param[in] cont The container to iterate over.
  *  \returns A new generator which will iterate over the container.
- *  \see fpgen::from_tup
+ *  \see fpgen::from_tup, fpgen::enumerate
  */
 template <typename T, typename... TArgs,
           template <typename...> typename Container>
@@ -31,6 +31,31 @@ generator<T> from(const Container<T, TArgs...> &cont) {
   }
 }
 
+/**
+ *  \brief Creates a generator over a data source, with indexing.
+ *
+ *  The data source does not have to allow indexing, but it is recommended for
+ * repeatable behaviour. If the index is not needed, use fpgen::from. The data
+ * source should support iterating (using `std::begin` and `std::end`).
+ *
+ *  \tparam T The type contained in the container.
+ *  \tparam TArgs Any other template parameters passed to the container.
+ *  \tparam Container The container type.
+ *  \param[in] cont The container to iterate over.
+ *  \returns A new generator which will iterate over the container using index
+ * and value.
+ * \see fpgen::from_tup, fpgen::enumerate
+ */
+template <typename T, typename... TArgs,
+          template <typename...> typename Container>
+generator<std::tuple<size_t, T>> enumerate(const Container<T, TArgs...> &cont) {
+  size_t i = 0;
+  for (auto it = std::begin(cont); it != std::end(cont); ++it) {
+    co_yield {i, *it};
+    i++;
+  }
+}
+
 /**
  *  \brief Creates a generator over an associative data source.
  *

test/src/test_sources.cpp

@@ -28,6 +28,16 @@ TEST(sources, from_set) {
   EXPECT_TRUE(todo.empty());
 }
 
+TEST(sources, enumerate_vector) {
+  std::vector<char> values = { 'a', 'c', 'e', 'k', 'j', 't' };
+  size_t prev = 0;
+  for(auto v : fpgen::enumerate(values)) {
+    EXPECT_EQ(std::get<0>(v), prev);
+    EXPECT_EQ(values[prev], std::get<1>(v));
+    prev++;
+  }
+}
+
 TEST(sources, from_map_tup) {
   std::map<std::string, std::string> map = {{"key 1", "value 1"},
                                             {"key 2", "value 2"},