Add String_view, a mutable string view

Add header <jegp/String_view.hpp> for defining String_view.
Numerate specification clauses.

README.md

@@ -6,14 +6,17 @@ Generic library components for my C++ projects.
 
 * A partial implementation of the upcoming standard following C++14
     - Variable type traits
+* Technical Specifications
+    - Library Fundamentals
+        + `<experimental/string_view>`
 
 ## Specification
 
 This project uses [Semantic Versioning 2.0.0](http://semver.org/spec/v2.0.0.html).
 
 This specification is the public API.
 
-### Header `<jegp/utility.hpp>` synopsis
+### 1 Header `<jegp/utility.hpp>` synopsis
 
 ```C++
 namespace jegp {
@@ -24,7 +27,7 @@ constexpr auto underlying_value(Enum e) noexcept;
 } // jegp namespace
 ```
 
-#### `underlying_value`
+#### 1.1 `underlying_value`
 
 Casts an enumeration value to its underlying type.
 
@@ -34,3 +37,121 @@ constexpr auto underlying_value(Enum e) noexcept;
 ```
 Returns: `static_cast<std::underlying_type_t<Enum>>(e)`.<br/>
 Remarks: This function shall not participate in overload resolution unless `std::is_enum_v<Enum>` is `true`.
+
+### 2 Header `<jegp/String_view.hpp>` synopsis
+
+```C++
+#include <experimental/string_view>
+
+namespace jegp {
+
+class String_view;
+
+} // jegp namespace
+```
+
+#### 2.1 Class `String_view`
+
+A mutable string view.
+
+```C++
+class String_view : public std::experimental::string_view {
+    using Base = std::experimental::string_view; // exposition only
+public:
+    constexpr String_view() noexcept = default;
+    constexpr String_view(char* str);
+    constexpr String_view(char* str, size_type len);
+
+    using iterator = pointer;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+
+    using Base::begin;
+    using Base::end;
+    constexpr iterator begin() noexcept;
+    constexpr iterator end() noexcept;
+
+    using Base::rbegin;
+    using Base::rend;
+    reverse_iterator rbegin() noexcept;
+    reverse_iterator rend() noexcept;
+
+    using Base::operator[];
+    using Base::at;
+    constexpr reference operator[](size_type pos);
+    constexpr reference at(size_type pos);
+
+    using Base::front;
+    using Base::back;
+    constexpr reference front();
+    constexpr reference back();
+
+    using Base::data;
+    constexpr pointer data() noexcept;
+
+    constexpr String_view substr(size_type pos = 0, size_type n = npos) const;
+};
+```
+
+##### 2.1.1 Construction
+
+```C++
+constexpr String_view(char* str);
+constexpr String_view(char* str, size_type len);
+```
+Effects: Initializes the base with the same argument list.
+
+##### 2.1.2 Iterator support
+
+```C++
+constexpr iterator begin() noexcept;
+```
+Returns: `data()`.
+
+```C++
+constexpr iterator end() noexcept;
+```
+Returns: `begin() + size()`.
+
+```C++
+reverse_iterator rbegin() noexcept;
+```
+Returns: `reverse_iterator{end()}`.
+
+```C++
+reverse_iterator rend() noexcept;
+```
+Returns: `reverse_iterator{begin()}`.
+
+##### 2.1.3 Element access
+
+```C++
+constexpr reference operator[](size_type pos);
+```
+Effects: Equivalent to `return const_cast<reference>(Base::operator[](pos));`.
+
+```C++
+constexpr reference at(size_type pos);
+```
+Effects: Equivalent to `return const_cast<reference>(Base::at(pos));`.
+
+```C++
+constexpr reference front();
+```
+Effects: Equivalent to `return const_cast<reference>(Base::front());`.
+
+```C++
+constexpr reference back();
+```
+Effects: Equivalent to `return const_cast<reference>(Base::back());`.
+
+```C++
+constexpr pointer data() noexcept;
+```
+Returns: `const_cast<pointer>(Base::data())`.
+
+##### 2.1.4 String operations
+
+```C++
+constexpr String_view substr(size_type pos = 0, size_type n = npos) const;
+```
+Returns: A string view that equals `Base{*this}.substr(pos,n)`.

include/jegp/String_view.hpp

@@ -0,0 +1,125 @@
+#ifndef JEGP_STRING_VIEW_HPP
+#define JEGP_STRING_VIEW_HPP
+
+#include <iterator>
+#include <experimental/string_view>
+
+namespace jegp {
+
+class String_view : public std::experimental::string_view {
+    using Base = std::experimental::string_view;
+
+    constexpr String_view(Base) noexcept;
+public:
+    constexpr String_view() noexcept = default;
+    constexpr String_view(char* str);
+    constexpr String_view(char* str, size_type len);
+
+    using iterator = pointer;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+
+    using Base::begin;
+    using Base::end;
+    constexpr iterator begin() noexcept;
+    constexpr iterator end() noexcept;
+
+    using Base::rbegin;
+    using Base::rend;
+    /*constexpr*/ reverse_iterator rbegin() noexcept;
+    /*constexpr*/ reverse_iterator rend() noexcept;
+
+    using Base::operator[];
+    using Base::at;
+    constexpr reference operator[](size_type pos);
+    constexpr reference at(size_type pos);
+
+    using Base::front;
+    using Base::back;
+    constexpr reference front();
+    constexpr reference back();
+
+    using Base::data;
+    constexpr pointer data() noexcept;
+
+    constexpr String_view substr(size_type pos = 0, size_type n = npos) const;
+};
+
+} // jegp namespace
+
+//------------------------------------------------------------------------------
+// "String_view.ipp" -----------------------------------------------------------
+//------------------------------------------------------------------------------
+
+namespace jegp {
+
+constexpr String_view::String_view(Base b) noexcept
+  : std::experimental::string_view{b}
+{
+}
+
+// Construction ----------------------------------------------------------------
+
+constexpr String_view::String_view(char* str)
+  : std::experimental::string_view{str}
+{
+}
+constexpr String_view::String_view(char* str, size_type len)
+  : std::experimental::string_view{str,len}
+{
+}
+
+// Iterator support ------------------------------------------------------------
+
+constexpr auto String_view::begin() noexcept -> iterator
+{
+    return data();
+}
+constexpr auto String_view::end() noexcept -> iterator
+{
+    return begin() + size();
+}
+
+inline /*constexpr*/ auto String_view::rbegin() noexcept -> reverse_iterator
+{
+    return reverse_iterator{end()};
+}
+inline /*constexpr*/ auto String_view::rend() noexcept -> reverse_iterator
+{
+    return reverse_iterator{begin()};
+}
+
+// Element access --------------------------------------------------------------
+
+constexpr auto String_view::operator[](size_type pos) -> reference
+{
+    return const_cast<reference>(Base::operator[](pos));
+}
+constexpr auto String_view::at(size_type pos) -> reference
+{
+    return const_cast<reference>(Base::at(pos));
+}
+
+constexpr auto String_view::front() -> reference
+{
+    return const_cast<reference>(Base::front());
+}
+constexpr auto String_view::back() -> reference
+{
+    return const_cast<reference>(Base::back());
+}
+
+constexpr auto String_view::data() noexcept -> pointer
+{
+    return const_cast<pointer>(Base::data());
+}
+
+// String operations -----------------------------------------------------------
+
+constexpr String_view String_view::substr(size_type pos, size_type n) const
+{
+    return Base::substr(pos,n);
+}
+
+} // jegp namespace
+
+#endif // JEGP_STRING_VIEW_HPP