Rename ranget::value_typet to ranget::value_type

Algorithms which are written expecting a STL container may reference a
`value_type` member, as this is the name of the member in STL
containers. Therefore this needs to be named the same way in `ranget` in
order to be compatible with such algorithms.

This commit includes a unit test of `ranget` having correct the
`value_type` defined.

Author: thomasspriggs

src/util/range.h

@@ -311,14 +311,14 @@ template <typename iteratort>
 struct ranget final
 {
 public:
-  using value_typet = typename iteratort::value_type;
+  using value_type = typename iteratort::value_type;
 
   ranget(iteratort begin, iteratort end) : begin_value(begin), end_value(end)
   {
   }
 
   ranget<filter_iteratort<iteratort>>
-  filter(std::function<bool(const value_typet &)> f)
+  filter(std::function<bool(const value_type &)> f)
   {
     auto shared_f = std::make_shared<decltype(f)>(std::move(f));
     filter_iteratort<iteratort> filter_begin(shared_f, begin(), end());
@@ -335,9 +335,9 @@ struct ranget final
   template <typename functiont>
   auto map(functiont &&f) -> ranget<map_iteratort<
     iteratort,
-    typename std::result_of<functiont(value_typet)>::type>>
+    typename std::result_of<functiont(value_type)>::type>>
   {
-    using outputt = typename std::result_of<functiont(value_typet)>::type;
+    using outputt = typename std::result_of<functiont(value_type)>::type;
     auto shared_f = std::make_shared<
       std::function<outputt(const typename iteratort::value_type &)>>(
       std::forward<functiont>(f));

unit/util/range.cpp

@@ -11,6 +11,14 @@ Author: Romain Brenguier, [email protected]
 #include <testing-utils/catch.hpp>
 #include <util/range.h>
 
+/// Trivial example template function requiring a container to have a
+/// `value_type`.
+template <typename containert>
+typename containert::value_type front(containert container)
+{
+  return *container.begin();
+}
+
 SCENARIO("range tests", "[core][util][range]")
 {
   GIVEN("A vector with three strings")
@@ -75,6 +83,18 @@ SCENARIO("range tests", "[core][util][range]")
       const std::vector<int> expected_odds{1, 3};
       REQUIRE(odds == expected_odds);
     }
+    THEN(
+      "The unit testing template function requiring `value_type` works with "
+      "`std::vector`.")
+    {
+      REQUIRE(front(input) == 1);
+    }
+    THEN(
+      "A range can be used with a template function expecting a container "
+      "which has a `value_type`.")
+    {
+      REQUIRE(front(make_range(input)) == 1);
+    }
   }
   GIVEN("Two const vectors of ints")
   {