C++ Format v6.1.0

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C++ Format v6.1.0 Release Notes

• • ✅ {fmt} now formats IEEE 754 float and double using the shortest decimal representation with correct rounding by default:

  .. code:: c++

   #include <cmath>
   #include <fmt/core.h>
  
   int main() {
     fmt::print("{}", M_PI);
   }
  

  prints 3.141592653589793.

  • 0️⃣ Made the fast binary to decimal floating-point formatter the default, simplified it and improved performance. {fmt} is now 15 times faster than libc++'s std::ostringstream, 11 times faster than printf and 10% faster than double-conversion on dtoa-benchmark <https://github.com/fmtlib/dtoa-benchmark>_:

  ================== ========= ======= Function Time (ns) Speedup ================== ========= ======= ostringstream 1,346.30 1.00x ostrstream 1,195.74 1.13x sprintf 995.08 1.35x doubleconv 99.10 13.59x fmt 88.34 15.24x ================== ========= =======

  .. image:: https://user-images.githubusercontent.com/576385/ 69767160-cdaca400-112f-11ea-9fc5-347c9f83caad.png

  • {fmt} no longer converts float arguments to double. In particular this improves the default (shortest) representation of floats and makes fmt::format consistent with std::format specs (#1336 <https://github.com/fmtlib/fmt/issues/1336>, #1353 <https://github.com/fmtlib/fmt/issues/1353>, #1360 <https://github.com/fmtlib/fmt/pull/1360>, #1361 <https://github.com/fmtlib/fmt/pull/1361>):

  .. code:: c++

   fmt::print("{}", 0.1f);
  

  prints 0.1 instead of 0.10000000149011612.

  Thanks @orivej (Orivej Desh) <https://github.com/orivej>_.

  • 🖨 Made floating-point formatting output consistent with printf/iostreams (#1376 <https://github.com/fmtlib/fmt/issues/1376>, #1417 <https://github.com/fmtlib/fmt/issues/1417>).

  • ➕ Added support for 128-bit integers (#1287 <https://github.com/fmtlib/fmt/pull/1287>_):

  .. code:: c++

   fmt::print("{}", std::numeric_limits<__int128_t>::max());
  

  prints 170141183460469231731687303715884105727.

  Thanks @denizevrenci (Deniz Evrenci) <https://github.com/denizevrenci>_.

  • 💅 The overload of print that takes text_style is now atomic, i.e. the output from different threads doesn't interleave (#1351 <https://github.com/fmtlib/fmt/pull/1351>). Thanks @tankiJong (Tanki Zhang) <https://github.com/tankiJong>.

  • Made compile time in the header-only mode ~20% faster by reducing the number of template instantiations. wchar_t overload of vprint was moved from fmt/core.h to fmt/format.h.

  • ➕ Added an overload of fmt::join that works with tuples (#1322 <https://github.com/fmtlib/fmt/issues/1322>, #1330 <https://github.com/fmtlib/fmt/pull/1330>):

  .. code:: c++

   #include <tuple>
   #include <fmt/ranges.h>
  
   int main() {
     std::tuple<char, int, float> t{'a', 1, 2.0f};
     fmt::print("{}", t);
   }
  

  prints ('a', 1, 2.0).

  Thanks @jeremyong (Jeremy Ong) <https://github.com/jeremyong>_.

  • 🔄 Changed formatting of octal zero with prefix from "00" to "0":

  .. code:: c++

   fmt::print("{:#o}", 0);
  

  prints 0.

  • The locale is now passed to ostream insertion (<<) operators (#1406 <https://github.com/fmtlib/fmt/pull/1406>_):

  .. code:: c++

   #include <fmt/locale.h>
   #include <fmt/ostream.h>
  
   struct S {
     double value;
   };
  
   std::ostream& operator<<(std::ostream& os, S s) {
     return os << s.value;
   }
  
   int main() {
     auto s = fmt::format(std::locale("fr_FR.UTF-8"), "{}", S{0.42});
     // s == "0,42"
   }
  

  Thanks @dlaugt (Daniel Laügt) <https://github.com/dlaugt>_.

  • Locale-specific number formatting now uses grouping (#1393 <https://github.com/fmtlib/fmt/issues/1393>_ #1394 <https://github.com/fmtlib/fmt/pull/1394>). Thanks @skrdaniel <https://github.com/skrdaniel>.

  • 🛠 Fixed handling of types with deleted implicit rvalue conversion to const char** (#1421 <https://github.com/fmtlib/fmt/issues/1421>_):

  .. code:: c++

   struct mystring {
     operator const char*() const&;
     operator const char*() &;
     operator const char*() const&& = delete;
     operator const char*() && = delete;
   };
   mystring str;
   fmt::print("{}", str); // now compiles
  

  • Enums are now mapped to correct underlying types instead of int (#1286 <https://github.com/fmtlib/fmt/pull/1286>). Thanks @agmt (Egor Seredin) <https://github.com/agmt>.

  • Enum classes are no longer implicitly converted to int (#1424 <https://github.com/fmtlib/fmt/issues/1424>_).

  • Added basic_format_parse_context for consistency with C++20 std::format and deprecated basic_parse_context.

  • 🛠 Fixed handling of UTF-8 in precision (#1389 <https://github.com/fmtlib/fmt/issues/1389>, #1390 <https://github.com/fmtlib/fmt/pull/1390>). Thanks @tajtiattila (Attila Tajti) <https://github.com/tajtiattila>_.

  • 🍎 {fmt} can now be installed on Linux, macOS and Windows with Conda <https://docs.conda.io/en/latest/>__ using its conda-forge <https://conda-forge.org>__ package <https://github.com/conda-forge/fmt-feedstock>__ (#1410 <https://github.com/fmtlib/fmt/pull/1410>_)::

    conda install -c conda-forge fmt

  Thanks @tdegeus (Tom de Geus) <https://github.com/tdegeus>_.

  • ➕ Added a CUDA test (#1285 <https://github.com/fmtlib/fmt/pull/1285>, #1317 <https://github.com/fmtlib/fmt/pull/1317>). Thanks @luncliff (Park DongHa) <https://github.com/luncliff>_ and @risa2000 <https://github.com/risa2000>_.

  • 👌 Improved documentation (#1276 <https://github.com/fmtlib/fmt/pull/1276>, #1291 <https://github.com/fmtlib/fmt/issues/1291>, #1296 <https://github.com/fmtlib/fmt/issues/1296>, #1315 <https://github.com/fmtlib/fmt/pull/1315>, #1332 <https://github.com/fmtlib/fmt/pull/1332>, #1337 <https://github.com/fmtlib/fmt/pull/1337>, #1395 <https://github.com/fmtlib/fmt/issues/1395>_ #1418 <https://github.com/fmtlib/fmt/pull/1418>). Thanks @waywardmonkeys (Bruce Mitchener) <https://github.com/waywardmonkeys>, @pauldreik (Paul Dreik) <https://github.com/pauldreik>, @jackoalan (Jack Andersen) <https://github.com/jackoalan>.

  • Various code improvements (#1358 <https://github.com/fmtlib/fmt/pull/1358>, #1407 <https://github.com/fmtlib/fmt/pull/1407>). Thanks @orivej (Orivej Desh) <https://github.com/orivej>, @dpacbach (David P. Sicilia) <https://github.com/dpacbach>,

  • 🛠 Fixed compile-time format string checks for user-defined types (#1292 <https://github.com/fmtlib/fmt/issues/1292>_).

  • Worked around a false positive in unsigned-integer-overflow sanitizer (#1377 <https://github.com/fmtlib/fmt/issues/1377>_).

  • 🛠 Fixed various warnings and compilation issues (#1273 <https://github.com/fmtlib/fmt/issues/1273>, #1278 <https://github.com/fmtlib/fmt/pull/1278>, #1280 <https://github.com/fmtlib/fmt/pull/1280>, #1281 <https://github.com/fmtlib/fmt/issues/1281>, #1288 <https://github.com/fmtlib/fmt/issues/1288>, #1290 <https://github.com/fmtlib/fmt/pull/1290>, #1301 <https://github.com/fmtlib/fmt/pull/1301>, #1305 <https://github.com/fmtlib/fmt/issues/1305>, #1306 <https://github.com/fmtlib/fmt/issues/1306>, #1309 <https://github.com/fmtlib/fmt/issues/1309>, #1312 <https://github.com/fmtlib/fmt/pull/1312>, #1313 <https://github.com/fmtlib/fmt/issues/1313>, #1316 <https://github.com/fmtlib/fmt/issues/1316>, #1319 <https://github.com/fmtlib/fmt/issues/1319>, #1320 <https://github.com/fmtlib/fmt/pull/1320>, #1326 <https://github.com/fmtlib/fmt/pull/1326>, #1328 <https://github.com/fmtlib/fmt/pull/1328>, #1344 <https://github.com/fmtlib/fmt/issues/1344>, #1345 <https://github.com/fmtlib/fmt/pull/1345>, #1347 <https://github.com/fmtlib/fmt/pull/1347>, #1349 <https://github.com/fmtlib/fmt/pull/1349>, #1354 <https://github.com/fmtlib/fmt/issues/1354>, #1362 <https://github.com/fmtlib/fmt/issues/1362>, #1366 <https://github.com/fmtlib/fmt/issues/1366>, #1364 <https://github.com/fmtlib/fmt/pull/1364>, #1370 <https://github.com/fmtlib/fmt/pull/1370>, #1371 <https://github.com/fmtlib/fmt/pull/1371>, #1385 <https://github.com/fmtlib/fmt/issues/1385>, #1388 <https://github.com/fmtlib/fmt/issues/1388>, #1397 <https://github.com/fmtlib/fmt/pull/1397>, #1414 <https://github.com/fmtlib/fmt/pull/1414>, #1416 <https://github.com/fmtlib/fmt/pull/1416>, #1422 <https://github.com/fmtlib/fmt/issues/1422>_ #1427 <https://github.com/fmtlib/fmt/pull/1427>, #1431 <https://github.com/fmtlib/fmt/issues/1431>, #1433 <https://github.com/fmtlib/fmt/pull/1433>). Thanks @hhb <https://github.com/hhb>, @gsjaardema (Greg Sjaardema) <https://github.com/gsjaardema>, @gabime (Gabi Melman) <https://github.com/gabime>, @neheb (Rosen Penev) <https://github.com/neheb>, @vedranmiletic (Vedran Miletić) <https://github.com/vedranmiletic>, @dkavolis (Daumantas Kavolis) <https://github.com/dkavolis>, @mwinterb <https://github.com/mwinterb>, @orivej (Orivej Desh) <https://github.com/orivej>, @denizevrenci (Deniz Evrenci) <https://github.com/denizevrenci> @leonklingele <https://github.com/leonklingele>, @chronoxor (Ivan Shynkarenka) <https://github.com/chronoxor>, @kent-tri <https://github.com/kent-tri>, @0x8000-0000 (Florin Iucha) <https://github.com/0x8000-0000>, @marti4d (Chris Martin) <https://github.com/marti4d>_.

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