format.h

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/* *****************************************************************************
 * kblib is a general utility library for C++14 and C++17, intended to provide
 * performant high-level abstractions and more expressive ways to do simple
 * things.
 *
 * Copyright (c) 2021 killerbee
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 * ****************************************************************************/
 
#ifndef KBLIB_FORMAT_H
#define KBLIB_FORMAT_H
 
#include "fakestd.h"
 
#include <algorithm>
#include <cmath>
 
namespace KBLIB_NS {
 
template <typename Number>
constexpr auto count_digits(Number val)
    -> enable_if_t<std::is_floating_point<Number>::value, int> {
   if (val == 0) {
      return 1;
   } else {
      return std::numeric_limits<Number>::digits10;
   }
}
 
template <typename Number>
constexpr auto count_digits(Number val)
    -> enable_if_t<not std::is_floating_point<Number>::value
                       and std::is_signed<Number>::value,
                   int> {
   if (val == 0 or val == 1) {
      return 1;
   } else {
      return static_cast<int>(std::ceil(
                 std::nextafter(std::log10(std::fabs(val)), INFINITY)))
             + (val < 0);
   }
}
 
template <typename Number>
constexpr auto count_digits(Number val)
    -> enable_if_t<std::is_unsigned<Number>::value, int> {
   if (val == 0) {
      return 1;
   } else if (val == static_cast<Number>(-1)) {
      return static_cast<int>(std::ceil(std::log10(val)));
   } else {
      return static_cast<int>(std::ceil(std::log10(val + 1)));
   }
}
 
template <typename Number>
constexpr auto count_digits(Number val, int base) -> int {
   if (val == 0) {
      return 1;
   } else if (std::is_floating_point<Number>::value) {
      return static_cast<int>(
          std::ceil(std::numeric_limits<Number>::digits * std::logb(base)));
   } else {
      return static_cast<int>(
                 std::ceil(std::log(std::abs(val) + 1) / std::log(base)))
             + (val < 0);
   }
}
 
template <typename ForwardIt>
constexpr auto max_count_digits(ForwardIt first, ForwardIt last) -> int {
   if (first == last) {
      return 0;
   }
   return count_digits(*std::max_element(first, last));
}
 
template <typename ForwardIt>
constexpr auto max_count_digits(ForwardIt first, ForwardIt last,
                                int base) -> int {
   if (first == last) {
      return 0;
   }
   return count_digits(*std::max_element(first, last), base);
}
 
} // namespace KBLIB_NS
 
#endif // KBLIB_FORMAT_H