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/**
* to_string.hpp - Provides compile-time integer-to-string conversion.
* Written by Clyne Sullivan.
* https://github.com/tcsullivan/constexpr-to-string
*/
#ifndef TCSULLIVAN_TO_STRING_HPP_
#define TCSULLIVAN_TO_STRING_HPP_
#include <type_traits>
/**
* @struct to_string_t
* @brief Provides the ability to convert any integral to a string at compile-time.
* @tparam N Number to convert
* @tparam base Desired base, can be from 2 to 36
*/
template<auto N, unsigned int base,
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 {
// The lambda calculates what the string length of N will be, so that `buf`
// fits to the number perfectly.
char buf[([] {
unsigned int len = N >= 0 ? 1 : 2;
for (auto n = N < 0 ? -N : N; n; len++, n /= base);
return len;
}())];
/**
* Constructs the object, filling `buf` with the string representation of N.
*/
constexpr to_string_t() {
auto ptr = buf + sizeof(buf) / sizeof(buf[0]);
*--ptr = '\0';
for (auto n = N < 0 ? -N : N; n; n /= base)
*--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[n % base];
if (N < 0)
*--ptr = '-';
}
/**
* Allows implicit conversion of this object to a `char *`.
*/
constexpr operator char *() {
return buf;
}
/**
* Allows implicit conversion of this object to a `const char *`.
*/
constexpr operator const char *() const {
return buf;
}
};
/**
* Simplifies use of `to_string_t` from `to_string_t<N>()` to `to_string<N>`.
*/
template<auto N, unsigned int base = 10>
to_string_t<N, base> to_string;
#endif // TCSULLIVAN_TO_STRING_HPP_
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