add value_type size_type for string_span (#727)
diff --git a/include/gsl/string_span b/include/gsl/string_span
index b5dfd18..85112e5 100644
--- a/include/gsl/string_span
+++ b/include/gsl/string_span
@@ -175,6 +175,7 @@
{
public:
using element_type = CharT;
+ using value_type = std::remove_cv_t<element_type>;
using pointer = std::add_pointer_t<element_type>;
using reference = std::add_lvalue_reference_t<element_type>;
using const_reference = std::add_lvalue_reference_t<std::add_const_t<element_type>>;
@@ -186,6 +187,8 @@
using reverse_iterator = typename impl_type::reverse_iterator;
using const_reverse_iterator = typename impl_type::const_reverse_iterator;
+ using size_type = index_type;
+
// default (empty)
constexpr basic_string_span() noexcept = default;