clyne/constexpr-to-string
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container-like #4

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Neargye merged 1 commits from master into master 2020-06-27 18:14:44 -04:00
Conversation 1 Commits 1 Files Changed 1 +22 -11
1 changed files with 22 additions and 11 deletions
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33
to_string.hpp
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@ -18,15 +18,16 @@
template<auto N, unsigned int base, typename char_type,
std::enable_if_t<std::is_integral_v<decltype(N)>, int> = 0,
std::enable_if_t<(base > 1 && base < 37), int> = 0>
struct to_string_t {
class to_string_t {
// The lambda calculates what the string length of N will be, so that `buf`
// fits to the number perfectly.
char_type buf[([] {
char_type buf[([]() constexpr noexcept {
unsigned int len = N > 0 ? 1 : 2;
for (auto n = N < 0 ? -N : N; n; len++, n /= base);
return len;
}())] = {};
public:
/**
* Constructs the object, filling `buf` with the string representation of N.
*/
@ -44,14 +45,24 @@ struct to_string_t {
}
// Support implicit casting to `char *` or `const char *`.
constexpr operator char_type *() { return buf; }
constexpr operator const char_type *() const { return buf; }
// Support range-based for loops
constexpr auto begin() { return buf; }
constexpr auto begin() const { return buf; }
constexpr auto end() { return buf + sizeof(buf) / sizeof(buf[0]); }
constexpr auto end() const { return buf + sizeof(buf) / sizeof(buf[0]); }
constexpr operator char_type *() noexcept { return buf; }
constexpr operator const char_type *() const noexcept { return buf; }
constexpr auto size() const noexcept { return sizeof(buf) / sizeof(buf[0]); }
// Element access
constexpr auto data() noexcept { return buf; }
constexpr auto data() const noexcept { return buf; }
constexpr auto operator[](unsigned int i) noexcept { return buf[i]; }
constexpr auto operator[](unsigned int i) const noexcept { return buf[i]; }
constexpr auto front() noexcept { return buf[0]; }
constexpr auto front() const noexcept { return buf[0]; }
constexpr auto back() noexcept { return buf[size() - 1]; }
constexpr auto back() const noexcept { return buf[size() - 1]; }
// Iterators
constexpr auto begin() noexcept { return buf; }
constexpr auto begin() const noexcept { return buf; }
constexpr auto end() noexcept { return buf + size(); }
constexpr auto end() const noexcept { return buf + size(); }
};
/**
@ -59,5 +70,5 @@ struct to_string_t {
*/
template<auto N, unsigned int base = 10, typename char_type = char>
constexpr to_string_t<N, base, char_type> to_string;
#endif // TCSULLIVAN_TO_STRING_HPP_