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mborlandmborland
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Merge pull request #361 from cppalliance/to_string
Add to_string
2 parents 4b471db + 7f5142c commit 1296489

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+251
-22
lines changed

4 files changed

+251
-22
lines changed

‎include/boost/decimal/detail/io.hpp‎

Lines changed: 1 addition & 22 deletions
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@@ -11,6 +11,7 @@
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#include <boost/decimal/detail/parser.hpp>
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#include <boost/decimal/detail/attributes.hpp>
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#include <boost/decimal/detail/fenv_rounding.hpp>
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#include <boost/decimal/detail/to_string.hpp>
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#if !defined(BOOST_DECIMAL_DISABLE_CLIB)
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@@ -87,28 +88,6 @@ auto operator>>(std::basic_istream<charT, traits>& is, DecimalType& d)
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# pragma GCC diagnostic ignored "-Wformat-truncation"
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#endif
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namespace detail {
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template <typename DecimalType, typename Integer, std::enable_if_t<!std::is_same<DecimalType, decimal128>::value, bool> = true>
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void print_buffer(char* buffer, std::size_t buffer_size, const char* format, Integer significand)
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{
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std::snprintf(buffer, buffer_size, format, significand);
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}
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template <typename DecimalType, typename Integer, std::enable_if_t<std::is_same<DecimalType, decimal128>::value, bool> = true>
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void print_buffer(char* buffer, std::size_t buffer_size, const char*, Integer significand)
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{
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char local_buffer [64];
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const auto p {detail::emulated128_to_buffer(local_buffer, significand)};
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const auto print_size {static_cast<std::size_t>(local_buffer + 64 - p)};
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if (print_size <= buffer_size)
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{
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std::memcpy(buffer, p, print_size);
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}
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}
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} //namespace detail
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// 3.2.11 Formatted output
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template <typename charT, typename traits, BOOST_DECIMAL_DECIMAL_FLOATING_TYPE DecimalType>
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auto operator<<(std::basic_ostream<charT, traits>& os, const DecimalType& d)

‎include/boost/decimal/detail/to_string.hpp‎

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// Copyright 2023 Matt Borland
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// Distributed under the Boost Software License, Version 1.0.
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// https://www.boost.org/LICENSE_1_0.txt
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#ifndef BOOST_DECIMAL_DETAIL_TO_STRING
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#define BOOST_DECIMAL_DETAIL_TO_STRING
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#include <boost/decimal/fwd.hpp>
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#include <boost/decimal/detail/config.hpp>
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#include <boost/decimal/detail/type_traits.hpp>
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#include <boost/decimal/detail/parser.hpp>
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#include <boost/decimal/detail/attributes.hpp>
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#include <boost/decimal/detail/fenv_rounding.hpp>
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#include <boost/decimal/detail/concepts.hpp>
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#include <boost/decimal/detail/cmath/frexp10.hpp>
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#if !defined(BOOST_DECIMAL_DISABLE_CLIB)
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#include <cerrno>
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#include <cstring>
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#include <cinttypes>
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#include <limits>
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#include <ios>
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#include <iostream>
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#include <system_error>
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#include <type_traits>
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#include <string>
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namespace boost {
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namespace decimal {
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// GCC UBSAN warns of format truncation from the constexpr calculation of the format
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// This warning was added in GCC 7.1
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#if __GNUC__ >= 7
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# pragma GCC diagnostic push
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# pragma GCC diagnostic ignored "-Wformat-truncation"
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#endif
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namespace detail {
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template <typename DecimalType, typename Integer, std::enable_if_t<!std::is_same<DecimalType, decimal128>::value, bool> = true>
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void print_buffer(char* buffer, std::size_t buffer_size, const char* format, Integer significand)
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{
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std::snprintf(buffer, buffer_size, format, significand);
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}
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template <typename DecimalType, typename Integer, std::enable_if_t<std::is_same<DecimalType, decimal128>::value, bool> = true>
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void print_buffer(char* buffer, std::size_t buffer_size, const char*, Integer significand)
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{
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char local_buffer [64];
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const auto p {detail::emulated128_to_buffer(local_buffer, significand)};
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const auto print_size {static_cast<std::size_t>(local_buffer + 64 - p)};
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if (print_size <= buffer_size)
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{
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std::memcpy(buffer, p, print_size);
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}
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}
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} //namespace detail
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template <BOOST_DECIMAL_DECIMAL_FLOATING_TYPE DecimalType>
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auto to_string(DecimalType value) -> std::string
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{
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std::string res;
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const bool d_isneg {signbit(value)};
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if (issignaling(value))
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{
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if (d_isneg)
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{
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res += "-";
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}
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res += "nan(snan)";
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return res;
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}
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if (isnan(value)) // only quiet NaNs left
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{
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if (d_isneg)
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{
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res += "-nan(ind)";
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}
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else
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{
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res += "nan";
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}
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return res;
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}
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if (isinf(value))
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{
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if (d_isneg)
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{
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res += "-";
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}
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res += "inf";
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return res;
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}
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auto precision {std::numeric_limits<DecimalType>::digits10};
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char buffer[detail::precision_v<DecimalType> + 6] {}; // Sign + Precision + decimal point + e + sign + null terminator
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const bool isneg {value < 0};
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if (isneg)
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{
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res += "-";
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}
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constexpr auto format {std::is_same<DecimalType, decimal32>::value ? "%" PRIu32 : "%" PRIu64};
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int exp {};
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auto significand = frexp10(value, &exp);
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auto significand_digits {detail::num_digits(significand)};
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const bool reduced {significand_digits > precision};
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while (significand_digits > precision + 1)
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{
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significand /= 10;
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++exp;
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--significand_digits;
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}
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if (reduced)
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{
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exp += detail::fenv_round<DecimalType>(significand, isneg);
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}
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// Print the significand into the buffer so that we can insert the decimal point
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detail::print_buffer<DecimalType>(buffer, sizeof(buffer), format, significand);
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std::memmove(buffer + 2, buffer + 1, static_cast<std::size_t>(precision - 1));
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std::memset(buffer + 1, '.', 1);
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res += buffer;
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// Offset will adjust the exponent to compensate for adding the decimal point
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const auto offset {detail::num_digits(significand) - 1};
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if (offset == 0)
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{
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res += "0";
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}
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auto end_it {res.end()};
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--end_it;
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while (*end_it == '0')
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{
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--end_it;
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}
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if (*end_it == '.')
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{
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--end_it;
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}
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++end_it;
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if (end_it != res.end())
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{
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res.erase(end_it, res.end());
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}
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auto print_exp {exp + offset};
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if (print_exp != 0)
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{
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res += "e";
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if (print_exp < 0)
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{
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res += "-";
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print_exp = -print_exp;
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}
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else
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{
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res += "+";
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}
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if (print_exp < 10)
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{
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res += "0";
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}
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res += std::to_string(print_exp);
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}
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return res;
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}
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#if __GNUC__ >= 7
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# pragma GCC diagnostic pop
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#endif
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} //namespace decimal
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} //namespace boost
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#endif
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#endif //BOOST_DECIMAL_DETAIL_TO_STRING

‎test/Jamfile‎

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Original file line numberDiff line numberDiff line change
@@ -67,3 +67,4 @@ run test_strtod.cpp ;
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run test_tan.cpp ;
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run test_tanh.cpp ;
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run test_tgamma.cpp ;
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run test_to_string.cpp ;

‎test/test_to_string.cpp‎

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// Copyright 2023 Matt Borland
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// Distributed under the Boost Software License, Version 1.0.
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// https://www.boost.org/LICENSE_1_0.txt
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#include <boost/decimal.hpp>
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#include <boost/core/lightweight_test.hpp>
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using namespace boost::decimal;
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#if !defined(BOOST_DECIMAL_DISABLE_CLIB)
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template <BOOST_DECIMAL_DECIMAL_FLOATING_TYPE T>
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void test()
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{
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BOOST_TEST_EQ(to_string(T{1}), "1");
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BOOST_TEST_EQ(to_string(T{10}), "1e+01");
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BOOST_TEST_EQ(to_string(T{100}), "1e+02");
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BOOST_TEST_EQ(to_string(T{1000}), "1e+03");
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BOOST_TEST_EQ(to_string(T{10000}), "1e+04");
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BOOST_TEST_EQ(to_string(T{210000}), "2.1e+05");
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BOOST_TEST_EQ(to_string(T{2100000}), "2.1e+06");
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BOOST_TEST_EQ(to_string(T{21, 6, true}), "-2.1e+07");
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BOOST_TEST_EQ(to_string(T{211, 6, true}), "-2.11e+08");
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BOOST_TEST_EQ(to_string(T{2111, 6, true}), "-2.111e+09");
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BOOST_TEST_EQ(to_string(std::numeric_limits<T>::infinity()), "inf");
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BOOST_TEST_EQ(to_string(-std::numeric_limits<T>::infinity()), "-inf");
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BOOST_TEST_EQ(to_string(std::numeric_limits<T>::quiet_NaN()), "nan");
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BOOST_TEST_EQ(to_string(-std::numeric_limits<T>::quiet_NaN()), "-nan(ind)");
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BOOST_TEST_EQ(to_string(std::numeric_limits<T>::signaling_NaN()), "nan(snan)");
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BOOST_TEST_EQ(to_string(-std::numeric_limits<T>::signaling_NaN()), "-nan(snan)");
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}
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int main()
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{
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test<decimal32>();
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test<decimal64>();
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test<decimal128>();
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return boost::report_errors();
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}
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#else
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int main()
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{
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return 0;
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}
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#endif

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