| /* |
| Copyright (c) Marshall Clow 2017-2017. |
| |
| 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 |
| */ |
| |
| #include <new> // for placement new |
| #include <iostream> |
| #include <cstddef> // for NULL, std::size_t, std::ptrdiff_t |
| #include <cstring> // for std::strchr and std::strcmp |
| #include <cstdlib> // for std::malloc and std::free |
| #include <cstdio> // for EOF |
| |
| #include <boost/config.hpp> |
| #include <boost/utility/string_view.hpp> |
| |
| #if __cplusplus >= 201402L |
| struct constexpr_char_traits |
| { |
| typedef char char_type; |
| typedef int int_type; |
| typedef std::streamoff off_type; |
| typedef std::streampos pos_type; |
| typedef std::mbstate_t state_type; |
| |
| static void assign(char_type& c1, const char_type& c2) noexcept { c1 = c2; } |
| static constexpr bool eq(char_type c1, char_type c2) noexcept { return c1 == c2; } |
| static constexpr bool lt(char_type c1, char_type c2) noexcept { return c1 < c2; } |
| |
| static constexpr int compare(const char_type* s1, const char_type* s2, size_t n) noexcept; |
| static constexpr size_t length(const char_type* s) noexcept; |
| static constexpr const char_type* find(const char_type* s, size_t n, const char_type& a) noexcept; |
| static constexpr char_type* move(char_type* s1, const char_type* s2, size_t n) noexcept; |
| static constexpr char_type* copy(char_type* s1, const char_type* s2, size_t n) noexcept; |
| static constexpr char_type* assign(char_type* s, size_t n, char_type a) noexcept; |
| |
| static constexpr int_type not_eof(int_type c) noexcept { return eq_int_type(c, eof()) ? ~eof() : c; } |
| static constexpr char_type to_char_type(int_type c) noexcept { return char_type(c); } |
| static constexpr int_type to_int_type(char_type c) noexcept { return int_type(c); } |
| static constexpr bool eq_int_type(int_type c1, int_type c2) noexcept { return c1 == c2; } |
| static constexpr int_type eof() noexcept { return EOF; } |
| }; |
| |
| // yields: |
| // 0 if for each i in [0,n), X::eq(s1[i],s2[i]) is true; |
| // else, a negative value if, for some j in [0,n), X::lt(s1[j],s2[j]) is true and |
| // for each i in [0,j) X::eq(s2[i],s2[i]) is true; |
| // else a positive value. |
| constexpr int constexpr_char_traits::compare(const char_type* s1, const char_type* s2, size_t n) noexcept |
| { |
| for (; n != 0; --n, ++s1, ++s2) |
| { |
| if (lt(*s1, *s2)) |
| return -1; |
| if (lt(*s2, *s1)) |
| return 1; |
| } |
| return 0; |
| } |
| |
| // yields: the smallest i such that X::eq(s[i],charT()) is true. |
| constexpr size_t constexpr_char_traits::length(const char_type* s) noexcept |
| { |
| size_t len = 0; |
| for (; !eq(*s, char_type(0)); ++s) |
| ++len; |
| return len; |
| } |
| |
| typedef boost::basic_string_view<char, constexpr_char_traits> string_view; |
| |
| int main() |
| { |
| constexpr string_view sv1; |
| constexpr string_view sv2{"abc", 3}; // ptr, len |
| constexpr string_view sv3{"def"}; // ptr |
| |
| constexpr const char *s1 = ""; |
| constexpr const char *s2 = "abc"; |
| |
| static_assert( (sv1 == sv1), "" ); |
| |
| static_assert(!(sv1 == sv2), "" ); |
| static_assert( (sv1 != sv2), "" ); |
| static_assert( (sv1 < sv2), "" ); |
| static_assert( (sv1 <= sv2), "" ); |
| static_assert(!(sv1 > sv2), "" ); |
| static_assert(!(sv1 >= sv2), "" ); |
| |
| static_assert(!(s1 == sv2), "" ); |
| static_assert( (s1 != sv2), "" ); |
| static_assert( (s1 < sv2), "" ); |
| static_assert( (s1 <= sv2), "" ); |
| static_assert(!(s1 > sv2), "" ); |
| static_assert(!(s1 >= sv2), "" ); |
| |
| static_assert(!(sv1 == s2), "" ); |
| static_assert( (sv1 != s2), "" ); |
| static_assert( (sv1 < s2), "" ); |
| static_assert( (sv1 <= s2), "" ); |
| static_assert(!(sv1 > s2), "" ); |
| static_assert(!(sv1 >= s2), "" ); |
| |
| static_assert( sv1.compare(sv2) < 0, "" ); |
| static_assert( sv1.compare(sv1) == 0, "" ); |
| static_assert( sv3.compare(sv1) > 0, "" ); |
| |
| static_assert( sv1.compare(s2) < 0, "" ); |
| static_assert( sv1.compare(s1) == 0, "" ); |
| static_assert( sv3.compare(s1) > 0, "" ); |
| } |
| #endif |