/*
   Copyright (c) Marshall Clow 2012-2015.
   Copyright Beman Dawes 2015

   Distributed under the Boost Software License, Version 1.0. (See accompanying
   file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

    For more information, see http://www.boost.org

    Based on the StringRef implementation in LLVM (http://llvm.org) and
    N3422 by Jeffrey Yasskin
        http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2012/n3442.html
    Updated July 2015 to reflect the Library Fundamentals TS
        http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4480.html
*/

#ifndef STX_STRING_VIEW_HPP_INCLUDED
#define STX_STRING_VIEW_HPP_INCLUDED

#ifndef STX_NAMESPACE_NAME
#define STX_NAMESPACE_NAME stx
#endif

// libstdc++'s std::experimental::string_view requries C++14
#if !defined(STX_NO_STD_STRING_VIEW) && (__cplusplus < 201402)
#include <cstddef>
#if defined(__GLIBCXX__)
#define STX_NO_STD_STRING_VIEW
#endif
#endif

#if defined(__has_include) && !defined(STX_NO_STD_STRING_VIEW)
#if __has_include(<string_view>)
#include <string_view>
#define STX_HAVE_STD_STRING_VIEW 1
namespace STX_NAMESPACE_NAME {
using std::basic_string_view;
using std::string_view;
using std::u16string_view;
using std::u32string_view;
using std::wstring_view;
}
#elif __has_include(<experimental / string_view>)
#include <experimental/string_view>
#define STX_HAVE_STD_STRING_VIEW 1
namespace STX_NAMESPACE_NAME {
using std::experimental::basic_string_view;
using std::experimental::string_view;
using std::experimental::u16string_view;
using std::experimental::u32string_view;
using std::experimental::wstring_view;
}
#endif // (__has_include(<string_view>) ||
       // __has_include(<experimental/string_view>))
#endif // __has_include

#ifndef STX_HAVE_STD_STRING_VIEW

#include <algorithm>
#include <cstddef>
#include <cstring>
#include <iosfwd>
#include <iterator>
#include <stdexcept>
#include <string>

#if __cpp_constexpr >= 201304
#define STX_CONSTEXPR14 constexpr
#else
#define STX_CONSTEXPR14
#endif

namespace STX_NAMESPACE_NAME {

namespace detail {
//  A helper functor because sometimes we don't have lambdas
template <typename charT, typename traits> class string_view_traits_eq {
public:
  string_view_traits_eq(charT ch) : ch_(ch) {}
  bool operator()(charT val) const { return traits::eq(ch_, val); }
  charT ch_;
};
}

template <typename charT, typename traits = std::char_traits<charT>>
class basic_string_view {
public:
  // types
  typedef traits traits_type;
  typedef charT value_type;
  typedef charT* pointer;
  typedef const charT* const_pointer;
  typedef charT& reference;
  typedef const charT& const_reference;
  typedef const_pointer const_iterator; // impl-defined
  typedef const_iterator iterator;
  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
  typedef const_reverse_iterator reverse_iterator;
  typedef std::size_t size_type;
  typedef std::ptrdiff_t difference_type;
  static constexpr size_type npos = size_type(-1);

  // construct/copy
  constexpr basic_string_view() noexcept : ptr_(NULL), len_(0) {}

  // by defaulting these functions, basic_string_ref becomes
  //  trivially copy/move constructible.
  constexpr basic_string_view(const basic_string_view& rhs) noexcept = default;
#if 0
    : ptr_(rhs.ptr_), len_(rhs.len_) {}
#endif

  basic_string_view& operator=(const basic_string_view& rhs) noexcept = default;
#if 0
    {
        ptr_ = rhs.ptr_;
        len_ = rhs.len_;
        return *this;
        }
#endif

  template <typename Allocator>
  basic_string_view(
      const std::basic_string<charT, traits, Allocator>& str) noexcept
      : ptr_(str.data()), len_(str.length()) {}

  constexpr basic_string_view(const charT* str)
      : ptr_(str), len_(traits::length(str)) {}

  constexpr basic_string_view(const charT* str, size_type len)
      : ptr_(str), len_(len) {}

  // iterators
  constexpr const_iterator begin() const noexcept { return ptr_; }
  constexpr const_iterator cbegin() const noexcept { return ptr_; }
  constexpr const_iterator end() const noexcept { return ptr_ + len_; }
  constexpr const_iterator cend() const noexcept { return ptr_ + len_; }
  const_reverse_iterator rbegin() const noexcept {
    return const_reverse_iterator(end());
  }
  const_reverse_iterator crbegin() const noexcept {
    return const_reverse_iterator(end());
  }
  const_reverse_iterator rend() const noexcept {
    return const_reverse_iterator(begin());
  }
  const_reverse_iterator crend() const noexcept {
    return const_reverse_iterator(begin());
  }

  // capacity
  constexpr size_type size() const noexcept { return len_; }
  constexpr size_type length() const noexcept { return len_; }
  constexpr size_type max_size() const noexcept { return len_; }
  constexpr bool empty() const noexcept { return len_ == 0; }

  // element access
  constexpr const_reference operator[](size_type pos) const noexcept {
    return ptr_[pos];
  }

  constexpr const_reference at(size_t pos) const {
    return pos >= len_ ? throw std::out_of_range("stx::string_view::at")
                       : ptr_[pos];
    //             if ( pos >= len_ )
    //                 BOOST_THROW_EXCEPTION( std::out_of_range (
    //                 "stx::string_view::at" ) );
    //             return ptr_[pos];
  }

  constexpr const_reference front() const { return ptr_[0]; }
  constexpr const_reference back() const { return ptr_[len_ - 1]; }
  constexpr const_pointer data() const noexcept { return ptr_; }

  // modifiers
  void clear() noexcept { len_ = 0; } // Boost extension

  STX_CONSTEXPR14 void remove_prefix(size_type n) {
    if (n > len_)
      n = len_;
    ptr_ += n;
    len_ -= n;
  }

  STX_CONSTEXPR14 void remove_suffix(size_type n) {
    if (n > len_)
      n = len_;
    len_ -= n;
  }

  STX_CONSTEXPR14 void swap(basic_string_view& s) noexcept {
    std::swap(ptr_, s.ptr_);
    std::swap(len_, s.len_);
  }

// basic_string_view string operations
#ifndef BOOST_NO_CXX11_EXPLICIT_CONVERSION_OPERATORS
  template <typename Allocator>
  explicit operator std::basic_string<charT, traits, Allocator>() const {
    return std::basic_string<charT, traits, Allocator>(begin(), end());
  }
#endif

#ifndef BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS
  template <typename Allocator = std::allocator<charT>>
  std::basic_string<charT, traits, Allocator>
  to_string(const Allocator& a = Allocator()) const {
    return std::basic_string<charT, traits, Allocator>(begin(), end(), a);
  }
#else
  std::basic_string<charT, traits> to_string() const {
    return std::basic_string<charT, traits>(begin(), end());
  }

  template <typename Allocator>
  std::basic_string<charT, traits, Allocator>
  to_string(const Allocator& a) const {
    return std::basic_string<charT, traits, Allocator>(begin(), end(), a);
  }
#endif

  size_type copy(charT* s, size_type n, size_type pos = 0) const {
    if (pos > size())
      throw std::out_of_range("string_view::copy");
    size_type rlen = (std::min)(n, len_ - pos);
    // use std::copy(begin() + pos, begin() + pos + rlen, s) rather than
    // std::copy_n(begin() + pos, rlen, s) to support pre-C++11 standard
    // libraries
    std::copy(begin() + pos, begin() + pos + rlen, s);
    return rlen;
  }

  STX_CONSTEXPR14 basic_string_view substr(size_type pos,
                                           size_type n = npos) const {
    if (pos > size())
      throw std::out_of_range("string_view::substr");
    if (n == npos || pos + n > size())
      n = size() - pos;
    return basic_string_view(data() + pos, n);
  }

  STX_CONSTEXPR14 int compare(basic_string_view x) const noexcept {
    const int cmp = traits::compare(ptr_, x.ptr_, (std::min)(len_, x.len_));
    return cmp != 0 ? cmp : (len_ == x.len_ ? 0 : len_ < x.len_ ? -1 : 1);
  }

  STX_CONSTEXPR14 int compare(size_type pos1, size_type n1,
                              basic_string_view x) const noexcept {
    return substr(pos1, n1).compare(x);
  }

  STX_CONSTEXPR14 int compare(size_type pos1, size_type n1, basic_string_view x,
                              size_type pos2, size_type n2) const {
    return substr(pos1, n1).compare(x.substr(pos2, n2));
  }

  STX_CONSTEXPR14 int compare(const charT* x) const {
    return compare(basic_string_view(x));
  }

  STX_CONSTEXPR14 int compare(size_type pos1, size_type n1,
                              const charT* x) const {
    return substr(pos1, n1).compare(basic_string_view(x));
  }

  STX_CONSTEXPR14 int compare(size_type pos1, size_type n1, const charT* x,
                              size_type n2) const {
    return substr(pos1, n1).compare(basic_string_view(x, n2));
  }

  //  Searches
  constexpr bool starts_with(charT c) const noexcept { // Boost extension
    return !empty() && traits::eq(c, front());
  }

  constexpr bool starts_with(basic_string_view x) const
      noexcept { // Boost extension
    return len_ >= x.len_ && traits::compare(ptr_, x.ptr_, x.len_) == 0;
  }

  constexpr bool ends_with(charT c) const noexcept { // Boost extension
    return !empty() && traits::eq(c, back());
  }

  constexpr bool ends_with(basic_string_view x) const
      noexcept { // Boost extension
    return len_ >= x.len_ &&
           traits::compare(ptr_ + len_ - x.len_, x.ptr_, x.len_) == 0;
  }

  //  find
  STX_CONSTEXPR14 size_type find(basic_string_view s, size_type pos = 0) const
      noexcept {
    if (pos > size())
      return npos;
    if (s.empty())
      return pos;
    const_iterator iter = std::search(this->cbegin() + pos, this->cend(),
                                      s.cbegin(), s.cend(), traits::eq);
    return iter == this->cend() ? npos : std::distance(this->cbegin(), iter);
  }
  STX_CONSTEXPR14 size_type find(charT c, size_type pos = 0) const noexcept {
    return find(basic_string_view(&c, 1), pos);
  }
  STX_CONSTEXPR14 size_type find(const charT* s, size_type pos,
                                 size_type n) const noexcept {
    return find(basic_string_view(s, n), pos);
  }
  STX_CONSTEXPR14 size_type find(const charT* s, size_type pos = 0) const
      noexcept {
    return find(basic_string_view(s), pos);
  }

  //  rfind
  STX_CONSTEXPR14 size_type rfind(basic_string_view s,
                                  size_type pos = npos) const noexcept {
    if (len_ < s.len_)
      return npos;
    if (pos > len_ - s.len_)
      pos = len_ - s.len_;
    if (s.len_ == 0u) // an empty string is always found
      return pos;
    for (const charT* cur = ptr_ + pos;; --cur) {
      if (traits::compare(cur, s.ptr_, s.len_) == 0)
        return cur - ptr_;
      if (cur == ptr_)
        return npos;
    };
  }
  STX_CONSTEXPR14 size_type rfind(charT c, size_type pos = npos) const
      noexcept {
    return rfind(basic_string_view(&c, 1), pos);
  }
  STX_CONSTEXPR14 size_type rfind(const charT* s, size_type pos,
                                  size_type n) const noexcept {
    return rfind(basic_string_view(s, n), pos);
  }
  STX_CONSTEXPR14 size_type rfind(const charT* s, size_type pos = npos) const
      noexcept {
    return rfind(basic_string_view(s), pos);
  }

  //  find_first_of
  STX_CONSTEXPR14 size_type find_first_of(basic_string_view s,
                                          size_type pos = 0) const noexcept {
    if (pos >= len_ || s.len_ == 0)
      return npos;
    const_iterator iter = std::find_first_of(this->cbegin() + pos, this->cend(),
                                             s.cbegin(), s.cend(), traits::eq);
    return iter == this->cend() ? npos : std::distance(this->cbegin(), iter);
  }
  STX_CONSTEXPR14 size_type find_first_of(charT c, size_type pos = 0) const
      noexcept {
    return find_first_of(basic_string_view(&c, 1), pos);
  }
  STX_CONSTEXPR14 size_type find_first_of(const charT* s, size_type pos,
                                          size_type n) const noexcept {
    return find_first_of(basic_string_view(s, n), pos);
  }
  STX_CONSTEXPR14 size_type find_first_of(const charT* s,
                                          size_type pos = 0) const noexcept {
    return find_first_of(basic_string_view(s), pos);
  }

  //  find_last_of
  STX_CONSTEXPR14 size_type find_last_of(basic_string_view s,
                                         size_type pos = npos) const noexcept {
    if (s.len_ == 0u)
      return npos;
    if (pos >= len_)
      pos = 0;
    else
      pos = len_ - (pos + 1);
    const_reverse_iterator iter = std::find_first_of(
        this->crbegin() + pos, this->crend(), s.cbegin(), s.cend(), traits::eq);
    return iter == this->crend() ? npos
                                 : reverse_distance(this->crbegin(), iter);
  }
  STX_CONSTEXPR14 size_type find_last_of(charT c, size_type pos = npos) const
      noexcept {
    return find_last_of(basic_string_view(&c, 1), pos);
  }
  STX_CONSTEXPR14 size_type find_last_of(const charT* s, size_type pos,
                                         size_type n) const noexcept {
    return find_last_of(basic_string_view(s, n), pos);
  }
  STX_CONSTEXPR14 size_type find_last_of(const charT* s,
                                         size_type pos = npos) const noexcept {
    return find_last_of(basic_string_view(s), pos);
  }

  //  find_first_not_of
  STX_CONSTEXPR14 size_type find_first_not_of(basic_string_view s,
                                              size_type pos = 0) const
      noexcept {
    if (pos >= len_)
      return npos;
    if (s.len_ == 0)
      return pos;
    const_iterator iter = find_not_of(this->cbegin() + pos, this->cend(), s);
    return iter == this->cend() ? npos : std::distance(this->cbegin(), iter);
  }
  STX_CONSTEXPR14 size_type find_first_not_of(charT c, size_type pos = 0) const
      noexcept {
    return find_first_not_of(basic_string_view(&c, 1), pos);
  }
  STX_CONSTEXPR14 size_type find_first_not_of(const charT* s, size_type pos,
                                              size_type n) const noexcept {
    return find_first_not_of(basic_string_view(s, n), pos);
  }
  STX_CONSTEXPR14 size_type find_first_not_of(const charT* s,
                                              size_type pos = 0) const
      noexcept {
    return find_first_not_of(basic_string_view(s), pos);
  }

  //  find_last_not_of
  STX_CONSTEXPR14 size_type find_last_not_of(basic_string_view s,
                                             size_type pos = npos) const
      noexcept {
    if (pos >= len_)
      pos = len_ - 1;
    if (s.len_ == 0u)
      return pos;
    pos = len_ - (pos + 1);
    const_reverse_iterator iter =
        find_not_of(this->crbegin() + pos, this->crend(), s);
    return iter == this->crend() ? npos
                                 : reverse_distance(this->crbegin(), iter);
  }
  STX_CONSTEXPR14 size_type find_last_not_of(charT c,
                                             size_type pos = npos) const
      noexcept {
    return find_last_not_of(basic_string_view(&c, 1), pos);
  }
  STX_CONSTEXPR14 size_type find_last_not_of(const charT* s, size_type pos,
                                             size_type n) const noexcept {
    return find_last_not_of(basic_string_view(s, n), pos);
  }
  STX_CONSTEXPR14 size_type find_last_not_of(const charT* s,
                                             size_type pos = npos) const
      noexcept {
    return find_last_not_of(basic_string_view(s), pos);
  }

private:
  template <typename r_iter>
  size_type reverse_distance(r_iter first, r_iter last) const noexcept {
    // Portability note here: std::distance is not NOEXCEPT, but calling it with
    // a string_view::reverse_iterator will not throw.
    return len_ - 1 - std::distance(first, last);
  }

  template <typename Iterator>
  Iterator find_not_of(Iterator first, Iterator last, basic_string_view s) const
      noexcept {
    for (; first != last; ++first)
      if (0 == traits::find(s.ptr_, s.len_, *first))
        return first;
    return last;
  }

  const charT* ptr_;
  std::size_t len_;
};

//  Comparison operators
//  Equality
template <typename charT, typename traits>
inline bool operator==(basic_string_view<charT, traits> x,
                       basic_string_view<charT, traits> y) noexcept {
  if (x.size() != y.size())
    return false;
  return x.compare(y) == 0;
}

//  Inequality
template <typename charT, typename traits>
inline bool operator!=(basic_string_view<charT, traits> x,
                       basic_string_view<charT, traits> y) noexcept {
  if (x.size() != y.size())
    return true;
  return x.compare(y) != 0;
}

//  Less than
template <typename charT, typename traits>
inline bool operator<(basic_string_view<charT, traits> x,
                      basic_string_view<charT, traits> y) noexcept {
  return x.compare(y) < 0;
}

//  Greater than
template <typename charT, typename traits>
inline bool operator>(basic_string_view<charT, traits> x,
                      basic_string_view<charT, traits> y) noexcept {
  return x.compare(y) > 0;
}

//  Less than or equal to
template <typename charT, typename traits>
inline bool operator<=(basic_string_view<charT, traits> x,
                       basic_string_view<charT, traits> y) noexcept {
  return x.compare(y) <= 0;
}

//  Greater than or equal to
template <typename charT, typename traits>
inline bool operator>=(basic_string_view<charT, traits> x,
                       basic_string_view<charT, traits> y) noexcept {
  return x.compare(y) >= 0;
}

// "sufficient additional overloads of comparison functions"
template <typename charT, typename traits, typename Allocator>
inline bool
operator==(basic_string_view<charT, traits> x,
           const std::basic_string<charT, traits, Allocator>& y) noexcept {
  return x == basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits, typename Allocator>
inline bool operator==(const std::basic_string<charT, traits, Allocator>& x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) == y;
}

template <typename charT, typename traits>
inline bool operator==(basic_string_view<charT, traits> x,
                       const charT* y) noexcept {
  return x == basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits>
inline bool operator==(const charT* x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) == y;
}

template <typename charT, typename traits, typename Allocator>
inline bool
operator!=(basic_string_view<charT, traits> x,
           const std::basic_string<charT, traits, Allocator>& y) noexcept {
  return x != basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits, typename Allocator>
inline bool operator!=(const std::basic_string<charT, traits, Allocator>& x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) != y;
}

template <typename charT, typename traits>
inline bool operator!=(basic_string_view<charT, traits> x,
                       const charT* y) noexcept {
  return x != basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits>
inline bool operator!=(const charT* x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) != y;
}

template <typename charT, typename traits, typename Allocator>
inline bool
operator<(basic_string_view<charT, traits> x,
          const std::basic_string<charT, traits, Allocator>& y) noexcept {
  return x < basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits, typename Allocator>
inline bool operator<(const std::basic_string<charT, traits, Allocator>& x,
                      basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) < y;
}

template <typename charT, typename traits>
inline bool operator<(basic_string_view<charT, traits> x,
                      const charT* y) noexcept {
  return x < basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits>
inline bool operator<(const charT* x,
                      basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) < y;
}

template <typename charT, typename traits, typename Allocator>
inline bool
operator>(basic_string_view<charT, traits> x,
          const std::basic_string<charT, traits, Allocator>& y) noexcept {
  return x > basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits, typename Allocator>
inline bool operator>(const std::basic_string<charT, traits, Allocator>& x,
                      basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) > y;
}

template <typename charT, typename traits>
inline bool operator>(basic_string_view<charT, traits> x,
                      const charT* y) noexcept {
  return x > basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits>
inline bool operator>(const charT* x,
                      basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) > y;
}

template <typename charT, typename traits, typename Allocator>
inline bool
operator<=(basic_string_view<charT, traits> x,
           const std::basic_string<charT, traits, Allocator>& y) noexcept {
  return x <= basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits, typename Allocator>
inline bool operator<=(const std::basic_string<charT, traits, Allocator>& x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) <= y;
}

template <typename charT, typename traits>
inline bool operator<=(basic_string_view<charT, traits> x,
                       const charT* y) noexcept {
  return x <= basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits>
inline bool operator<=(const charT* x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) <= y;
}

template <typename charT, typename traits, typename Allocator>
inline bool
operator>=(basic_string_view<charT, traits> x,
           const std::basic_string<charT, traits, Allocator>& y) noexcept {
  return x >= basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits, typename Allocator>
inline bool operator>=(const std::basic_string<charT, traits, Allocator>& x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) >= y;
}

template <typename charT, typename traits>
inline bool operator>=(basic_string_view<charT, traits> x,
                       const charT* y) noexcept {
  return x >= basic_string_view<charT, traits>(y);
}

template <typename charT, typename traits>
inline bool operator>=(const charT* x,
                       basic_string_view<charT, traits> y) noexcept {
  return basic_string_view<charT, traits>(x) >= y;
}

namespace detail {

template <class charT, class traits>
inline void sv_insert_fill_chars(std::basic_ostream<charT, traits>& os,
                                 std::size_t n) {
  enum { chunk_size = 8 };
  charT fill_chars[chunk_size];
  std::fill_n(fill_chars, static_cast<std::size_t>(chunk_size), os.fill());
  for (; n >= chunk_size && os.good(); n -= chunk_size)
    os.write(fill_chars, static_cast<std::size_t>(chunk_size));
  if (n > 0 && os.good())
    os.write(fill_chars, n);
}

template <class charT, class traits>
void sv_insert_aligned(std::basic_ostream<charT, traits>& os,
                       const basic_string_view<charT, traits>& str) {
  const std::size_t size = str.size();
  const std::size_t alignment_size =
      static_cast<std::size_t>(os.width()) - size;
  const bool align_left =
      (os.flags() & std::basic_ostream<charT, traits>::adjustfield) ==
      std::basic_ostream<charT, traits>::left;
  if (!align_left) {
    detail::sv_insert_fill_chars(os, alignment_size);
    if (os.good())
      os.write(str.data(), size);
  } else {
    os.write(str.data(), size);
    if (os.good())
      detail::sv_insert_fill_chars(os, alignment_size);
  }
}

} // namespace detail

// Inserter
template <class charT, class traits>
inline std::basic_ostream<charT, traits>&
operator<<(std::basic_ostream<charT, traits>& os,
           const basic_string_view<charT, traits>& str) {
  if (os.good()) {
    const std::size_t size = str.size();
    const std::size_t w = static_cast<std::size_t>(os.width());
    if (w <= size)
      os.write(str.data(), size);
    else
      detail::sv_insert_aligned(os, str);
    os.width(0);
  }
  return os;
}

#if 0
// numeric conversions
    //
    //  These are short-term implementations.
    //  In a production environment, I would rather avoid the copying.
    //
    inline int stoi (string_view str, size_t* idx=0, int base=10) {
        return std::stoi ( std::string(str), idx, base );
        }

    inline long stol (string_view str, size_t* idx=0, int base=10) {
        return std::stol ( std::string(str), idx, base );
        }

    inline unsigned long stoul (string_view str, size_t* idx=0, int base=10) {
        return std::stoul ( std::string(str), idx, base );
        }

    inline long long stoll (string_view str, size_t* idx=0, int base=10) {
        return std::stoll ( std::string(str), idx, base );
        }

    inline unsigned long long stoull (string_view str, size_t* idx=0, int base=10) {
        return std::stoull ( std::string(str), idx, base );
        }

    inline float stof (string_view str, size_t* idx=0) {
        return std::stof ( std::string(str), idx );
        }

    inline double stod (string_view str, size_t* idx=0) {
        return std::stod ( std::string(str), idx );
        }

    inline long double stold (string_view str, size_t* idx=0)  {
        return std::stold ( std::string(str), idx );
        }

    inline int  stoi (wstring_view str, size_t* idx=0, int base=10) {
        return std::stoi ( std::wstring(str), idx, base );
        }

    inline long stol (wstring_view str, size_t* idx=0, int base=10) {
        return std::stol ( std::wstring(str), idx, base );
        }

    inline unsigned long stoul (wstring_view str, size_t* idx=0, int base=10) {
        return std::stoul ( std::wstring(str), idx, base );
        }

    inline long long stoll (wstring_view str, size_t* idx=0, int base=10) {
        return std::stoll ( std::wstring(str), idx, base );
        }

    inline unsigned long long stoull (wstring_view str, size_t* idx=0, int base=10) {
        return std::stoull ( std::wstring(str), idx, base );
        }

    inline float  stof (wstring_view str, size_t* idx=0) {
        return std::stof ( std::wstring(str), idx );
        }

    inline double stod (wstring_view str, size_t* idx=0) {
        return std::stod ( std::wstring(str), idx );
        }

    inline long double stold (wstring_view str, size_t* idx=0) {
        return std::stold ( std::wstring(str), idx );
        }
#endif

using string_view = basic_string_view<char, std::char_traits<char>>;
using u16string_view = basic_string_view<char16_t, std::char_traits<char16_t>>;
using u32string_view = basic_string_view<char32_t, std::char_traits<char32_t>>;
using wstring_view = basic_string_view<wchar_t, std::char_traits<wchar_t>>;

} // end namespace

#if 0
namespace std {
    // Hashing
    template<> struct hash<STX_NAMESPACE_NAME::string_view>;
    template<> struct hash<STX_NAMESPACE_NAME::u16string_view>;
    template<> struct hash<STX_NAMESPACE_NAME::u32string_view>;
    template<> struct hash<STX_NAMESPACE_NAME::wstring_view>;
}
#endif

#endif // STX_HAVE_STD_STRING_VIEW

#endif // STX_STRING_VIEW_HPP_INCLUDED
