Re: Implement N3762 string_view: a non-owning reference to a string.

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 15 November 2013 04:42, Ed Smith-Rowland wrote:
>
> As the title says.  It's a pretty simple class" a non-mutating read-only
> view into a const CharT* or a basic_string.

Nice, thanks.

+/** @file experimantal/string_view
+ *  This is a Standard C++ Library header.
+ */

s/experimantal/experimental/
The same doxygen header appears in string_view.tcc but shouldn't be
there (it should either have no doxygen @file block or should have a
"This is an internal header file, ..." block.

Can you use the same approach as std::array::at to make
basic_string_view::at constexpr?

basic_string_view::substr would need a constexpr std::min to use the
same technique.

_S_compare should be possible to make constexpr, I can look into that
once it's committed.

+  namespace __detail
+  {
+    //  Identiry transform to make ADL work with just one argument.
+    //  See n3766.html.
+    template<class _Tp=void>
+      struct __identity
+      { typedef _Tp type; };
+
+    template<>
+      struct __identity<void>;
+
+    template<class _Tp>
+      using __idt = typename __identity<_Tp>::type;
+  }

s/Identiry/Identity/ and please use typename _Tp instead of class _Tp
in the template parameter list.

+  template<typename _CharT, typename _Traits>
+    bool
+    operator==(basic_string_view<_CharT, _Traits> __x,
+               basic_string_view<_CharT, _Traits> __y) noexcept
+    { return __x.compare(__y) == 0; }
+  template<typename _CharT, typename _Traits>
+    bool
+    operator==(basic_string_view<_CharT, _Traits> __x,
+               __detail::__idt<basic_string_view<_CharT, _Traits>>
__y) noexcept
+    { return __x.compare(__y) == 0; }
+  template<typename _CharT, typename _Traits>
+    bool
+    operator==(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
+               basic_string_view<_CharT, _Traits> __y) noexcept
+    { return __x.compare(__y) == 0; }

Please add a blank line between these function templates.

I think the std::hash declaration and specializations should be inside
a _GLIBCXX_BEGIN_NAMESPACE_VERSION / _GLIBCXX_END_NAMESPACE_VERSION
pair, because when using versioned namespaces they will be in
std::__v7 not std.