clyne/constexpr-to-string
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Removing magic constant from template param check #3

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SecMeant merged 3 commits from digits_array into master 2020-06-29 15:17:39 -04:00
Conversation 8 Commits 3 Files Changed 2 +8 -3
2 changed files with 8 additions and 3 deletions
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4
README.md
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@ -48,11 +48,13 @@ The integer/string conversion is done using a simple method I learned over the y
(*Note: The below examples of code are not up-to-date, though they still give a general idea of how `to_string` works.*) (*Note: The below examples of code are not up-to-date, though they still give a general idea of how `to_string` works.*)
```cpp ```cpp
constexpr char digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
constexpr to_string_t() { constexpr to_string_t() {
auto ptr = buf + sizeof(buf) / sizeof(buf[0]); auto ptr = buf + sizeof(buf) / sizeof(buf[0]);
*--ptr = '\0'; *--ptr = '\0';
for (auto n = N < 0 ? -N : N; n; n /= base) for (auto n = N < 0 ? -N : N; n; n /= base)
*--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[n % base]; *--ptr = digits[n % base];
if (N < 0) if (N < 0)
*--ptr = '-'; *--ptr = '-';
} }

7
to_string.hpp
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@ -9,6 +9,9 @@
#include <type_traits> #include <type_traits>
constexpr char digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
constexpr auto digit_count = sizeof(digits) / sizeof(digits[0]);
Neargye commented 2020-06-27 12:20:45 -04:00 (Migrated from github.com)
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inline constexpr

`inline constexpr `
m-peko commented 2020-06-29 08:43:29 -04:00 (Migrated from github.com)
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@Neargye why inline constexpr when constexpr itself is implicitly inline?

@Neargye why `inline constexpr` when `constexpr` itself is implicitly inline?
Neargye commented 2020-06-29 08:47:46 -04:00 (Migrated from github.com)
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​constexpr specifier implies  inline for static data members as well as functions, but not for global variable.
https://en.cppreference.com/w/cpp/language/inline

​constexpr specifier implies  inline for static data members as well as functions, but not for global variable. https://en.cppreference.com/w/cpp/language/inline
/** /**
Neargye commented 2020-06-27 12:20:55 -04:00 (Migrated from github.com)
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also inline constexpr

also `inline constexpr`
* @struct to_string_t * @struct to_string_t
* @brief Provides the ability to convert any integral to a string at compile-time. * @brief Provides the ability to convert any integral to a string at compile-time.
@ -17,7 +20,7 @@
*/ */
template<auto N, unsigned int base, typename char_type, 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<std::is_integral_v<decltype(N)>, int> = 0,
std::enable_if_t<(base > 1 && base < 37), int> = 0> std::enable_if_t<(base > 1 && base < digit_count), int> = 0>
struct to_string_t { struct to_string_t {
// The lambda calculates what the string length of N will be, so that `buf` // The lambda calculates what the string length of N will be, so that `buf`
// fits to the number perfectly. // fits to the number perfectly.
@ -35,7 +38,7 @@ struct to_string_t {
auto ptr = buf + sizeof(buf) / sizeof(buf[0]); auto ptr = buf + sizeof(buf) / sizeof(buf[0]);
*--ptr = '\0'; *--ptr = '\0';
for (auto n = N < 0 ? -N : N; n; n /= base) for (auto n = N < 0 ? -N : N; n; n /= base)
*--ptr = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[n % base]; *--ptr = digits[n % base];
if (N < 0) if (N < 0)
*--ptr = '-'; *--ptr = '-';
} else { } else {