123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114 |
- /*
- 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 <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
|