Implement ranges with different boundary types

Implements #8.

Author: klmr

range.hpp

@@ -181,9 +181,10 @@ struct infinite_range_proxy {
     iterator begin_;
 };
 
-template <typename T>
-range_proxy<T> range(T begin, T end) {
-    return {begin, end};
+template <typename T, typename U>
+auto range(T begin, U end) -> range_proxy<typename std::common_type<T, U>::type> {
+    using C = typename std::common_type<T, U>::type;
+    return {static_cast<C>(begin), static_cast<C>(end)};
 }
 
 template <typename T>

test.cpp

@@ -64,6 +64,13 @@ int main() {
     print_range(range(8.0, 1.0).step(-2.0));
     cout << "\n";
 
+    cout << "Mixed type inference:\n";
+    print_range(range(0, sizeof "Hello"));
+    cout << "Inferred as mangled type name "
+        << typeid(typename std::iterator_traits<decltype(range(0, sizeof "Hello").begin())>::value_type).name()
+        << " (expected: " << typeid(decltype(sizeof "Hello")).name() << ")\n";
+    cout << "\n";
+
     test_range_size(range(1, 8).step(2));
     test_range_size(range(8.0, 1.0).step(-2.0));
     test_range_size(range(8, 1).step(-2));