Define C++20 concepts #848

mborland · 2022-10-16T22:14:07Z

@jzmaddock, @ckormanyos, and @NAThompson I am looking for some feedback on this PR. This defines new C++20esque concepts for our use, and abs.hpp shows both ways to call them to preserve existing SFINAE expressions. I think this would be useful to spread around the codebase to reduce nasty template errors once matured. Thanks for your help.

include/boost/math/concepts/concepts.hpp

jzmaddock · 2022-10-17T11:56:52Z

Some questions:

What is the impact on compile time of using concepts rather than SFINAE or nothing at all?
Can we do "sophisticated" concepts that model for example the requirements that the special functions and distributions require: https://github.com/boostorg/math/blob/develop/include/boost/math/concepts/real_concept.hpp without it exploding the compiler?
For the constexpr-math functions the requirements are much smaller, but we require constexpr arithmetic operators rather than is_floating_point as such. Again is this possible to check without exploding compile times?
How's current compiler support? Better than modules I hope!

I'm sure there are more detailed questions that will arise in time, we need to figure out what the general pro's and cons are first.

mborland · 2022-10-17T15:58:56Z

Some questions:

What is the impact on compile time of using concepts rather than SFINAE or nothing at all?

Concepts decrease compile times when replacing SFINAE expressions. I expect they will increase if we are replacing typename T with concept T, but haven't found any benchmarks for that

Can we do "sophisticated" concepts that model for example the requirements that the special functions and distributions require: https://github.com/boostorg/math/blob/develop/include/boost/math/concepts/real_concept.hpp without it exploding the compiler?

I'll play around with it today. If that doesn't work I was thinking about providing specializations of Boost.Type_Traits in each of Boost.Multiprecision types for both the MP type and it's underlying (if applicable). That would hit a lot of the major types additional types, and then offer some mechanism to disable BOOST_MATH_CONCEPTS for user rolled types that we have no knowledge of.

For the constexpr-math functions the requirements are much smaller, but we require constexpr arithmetic operators rather than is_floating_point as such. Again is this possible to check without exploding compile times?

I can add one of the special functions to this PR that runs on arbitrary types instead of just builtins as an example. Starting with the ccmath functions offered a simpler starting point.

How's current compiler support? Better than modules I hope!

All of the major compilers support concepts

I'm sure there are more detailed questions that will arise in time, we need to figure out what the general pro's and cons are first.

[ci skip]

mborland · 2022-10-17T20:21:58Z

Here's a small comparison of the impacts running ../../../b2 test_beta toolset=clang cxxstd=11,14,17,20

using current develop: 60.35s user 6.04s system 543% cpu 12.204 total
with concepts: 60.41s user 6.56s system 544% cpu 12.294 total

Obviously I should run this many more times to be scientific, but there is not obvious divergence between the two.

mborland · 2022-10-20T01:40:15Z

@jzmaddock and @NAThompson I think this is good for review and comments. ccmath/abs, beta, and univariate statistics have been converted to use concepts. As usual Apple's Clang needed some help, but everything is green on CI now.

jzmaddock · 2022-11-04T17:44:28Z

Thanks Matt, just pulling down the code to experiment with now...

…epts

jzmaddock · 2022-11-10T19:20:12Z

OK, just messing about with this, I'm seeing a small impact on compile times, which mostly seem to be coming from parsing the new header. I converted log1p.hpp as one of the smallest (most sensitive?) headers to try this out on, and only applied the concepts to the user-callable functions, ie not the code in the detail namespace as IMO that gains nothing from concept checks? Then with a trivial test program:

#include <boost/math/special_functions/log1p.hpp>
#include <iostream>

int main()
{
   using Real = double;
   Real d = boost::math::log1p(Real(2));

   return 0;
}

Build times with -O3 -std=c++20 and cygwin gcc were 4.4s with -DBOOST_MATH_DISABLE_CONCEPTS rising to 5s without the define. Including the new concepts.hpp header but without using them, saw similar compile times to where they were used, so at present this looks like a fixed cost of parsing the header.

jzmaddock · 2022-11-10T19:27:56Z

MSVC build times for the same example are a bit variable, but it looks like around 3s with -DBOOST_MATH_DISABLE_CONCEPTS rising to 4s without.

jzmaddock · 2022-11-10T19:39:28Z

Confirmed that error messages are much improved though: msvc is quite terse:

D:\data\boost\boost\t.cpp(12,26): error C2672: 'boost::math::log1p': no matching overloaded function found
D:\data\boost\boost\t.cpp(12,33): error C7602: 'boost::math::log1p': the associated constraints are not satisfied

While gcc gets a bit more verbose:

t.cpp: In function ‘int main()’:
t.cpp:12:31: error: no matching function for call to ‘log1p(std::string&)’
   12 |    Real d = boost::math::log1p(s);
      |             ~~~~~~~~~~~~~~~~~~^~~
In file included from t.cpp:4:
./boost/math/special_functions/log1p.hpp:429:46: note: candidate: ‘template<class T>  requires  arbitrary_real_type<T> typename boost::math::tools::promote_args<T>::type boost::math::log1p(T)’
  429 | inline typename tools::promote_args<T>::type log1p(T x)
      |                                              ^~~~~
./boost/math/special_functions/log1p.hpp:429:46: note:   template argument deduction/substitution failed:
./boost/math/special_functions/log1p.hpp:429:46: note: constraints not satisfied
In file included from ./boost/math/special_functions/math_fwd.hpp:32,
                 from ./boost/math/special_functions/log1p.hpp:23,
                 from t.cpp:4:
t.cpp: In substitution of ‘template<class T>  requires  arbitrary_real_type<T> typename boost::math::tools::promote_args<T>::type boost::math::log1p(T) [with T = std::basic_string<char>]’:
t.cpp:12:31:   required from here
./boost/math/concepts/concepts.hpp:143:9:   required for the satisfaction of ‘arbitrary_arithmetic_type<T>’ [with T = std::basic_string<char, std::char_traits<char>, std::allocator<char> >]
./boost/math/concepts/concepts.hpp:159:9:   required for the satisfaction of ‘arbitrary_real_type<T>’ [with T = std::basic_string<char, std::char_traits<char>, std::allocator<char> >]
./boost/math/concepts/concepts.hpp:143:75: note: no operand of the disjunction is satisfied
  143 | concept arbitrary_arithmetic_type = arbitrary_unsigned_arithmetic_type<T> ||
      |                                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
  144 |                                     arbitrary_signed_arithmetic_type<T>;
      |                                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: note: set ‘-fconcepts-diagnostics-depth=’ to at least 2 for more detail
In file included from t.cpp:4:
./boost/math/special_functions/log1p.hpp:298:46: note: candidate: ‘template<class T, class Policy>  requires (arbitrary_real_type<T>) && (policy<Policy>) typename boost::math::tools::promote_args<T>::type boost::math::log1p(T, const Policy&)’
  298 | inline typename tools::promote_args<T>::type log1p(T x, const Policy&)
      |                                              ^~~~~
./boost/math/special_functions/log1p.hpp:298:46: note:   template argument deduction/substitution failed:
t.cpp:12:31: note:   candidate expects 2 arguments, 1 provided
   12 |    Real d = boost::math::log1p(s);
      |             ~~~~~~~~~~~~~~~~~~^~~
In file included from t.cpp:4:
./boost/math/special_functions/log1p.hpp:332:14: note: candidate: ‘template<class Policy>  requires  policy<Policy> float boost::math::log1p(float, const Policy&)’
  332 | inline float log1p(float x, const Policy& pol)
      |              ^~~~~
./boost/math/special_functions/log1p.hpp:332:14: note:   template argument deduction/substitution failed:
t.cpp:12:31: note:   candidate expects 2 arguments, 1 provided
   12 |    Real d = boost::math::log1p(s);
      |             ~~~~~~~~~~~~~~~~~~^~~
In file included from t.cpp:4:
./boost/math/special_functions/log1p.hpp:344:20: note: candidate: ‘template<class Policy>  requires  policy<Policy> long double boost::math::log1p(long double, const Policy&)’
  344 | inline long double log1p(long double x, const Policy& pol)
      |                    ^~~~~
./boost/math/special_functions/log1p.hpp:344:20: note:   template argument deduction/substitution failed:
t.cpp:12:31: note:   candidate expects 2 arguments, 1 provided
   12 |    Real d = boost::math::log1p(s);
      |             ~~~~~~~~~~~~~~~~~~^~~
./boost/math/special_functions/log1p.hpp:369:15: note: candidate: ‘template<class Policy>  requires  policy<Policy> double boost::math::log1p(double, const Policy&)’
  369 | inline double log1p(double x, const Policy& pol)
      |               ^~~~~
./boost/math/special_functions/log1p.hpp:369:15: note:   template argument deduction/substitution failed:
t.cpp:12:31: note:   candidate expects 2 arguments, 1 provided
   12 |    Real d = boost::math::log1p(s);
      |             ~~~~~~~~~~~~~~~~~~^~~

mborland · 2022-11-11T04:07:40Z

@jzmaddock I would concur that we probably only need to implement concepts in the user facing functions and not in the detail namespace unless it will save us compile time by replacing SFINAE with concepts.

I think it is worth pointing out for posterity that passing a std::string to the current implementation of boost::math::log1p like in your example results in C++ standard template spaghetti:

garbage.cpp: In function 'int main()':
garbage.cpp:8:38: error: no matching function for call to 'std::__cxx11::basic_string<char>::basic_string(int)'
    8 |    Real d = boost::math::log1p(Real(2));
      |                                      ^
In file included from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/string:53,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/locale_classes.h:40,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/ios_base.h:41,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/streambuf:41,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/streambuf_iterator.h:35,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/iterator:66,
                 from ../../../boost/iterator/iterator_traits.hpp:10,
                 from ../../../boost/range/iterator_range_core.hpp:26,
                 from ../../../boost/lexical_cast.hpp:30,
                 from ../../../boost/math/tools/big_constant.hpp:12,
                 from ../../../boost/math/special_functions/log1p.hpp:21,
                 from garbage.cpp:1:
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:786:9: note: candidate: 'template<class _Tp, class> constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _Tp&, const _Alloc&) [with <template-parameter-2-2> = _Tp; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  786 |         basic_string(const _Tp& __t, const _Alloc& __a = _Alloc())
      |         ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:786:9: note:   template argument deduction/substitution failed:
In file included from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/stl_pair.h:60,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/stl_algobase.h:64,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/specfun.h:45,
                 from /opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/cmath:1935,
                 from ../../../boost/math/special_functions/log1p.hpp:15:
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/type_traits: In substitution of 'template<bool _Cond, class _Tp> using enable_if_t = typename std::enable_if::type [with bool _Cond = false; _Tp = void]':
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:155:8:   required by substitution of 'template<class _CharT, class _Traits, class _Alloc> template<class _Tp, class _Res> using _If_sv = std::enable_if_t<std::__and_<std::is_convertible<const _Tp&, std::basic_string_view<_CharT, _Traits> >, std::__not_<std::is_convertible<const _Tp*, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>*> >, std::__not_<std::is_convertible<const _Tp&, const _CharT*> > >::value, _Res> [with _Tp = int; _Res = void; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:783:30:   required from here
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/type_traits:2614:11: error: no type named 'type' in 'struct std::enable_if<false, void>'
 2614 |     using enable_if_t = typename enable_if<_Cond, _Tp>::type;
      |           ^~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:774:9: note: candidate: 'template<class _Tp, class> constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _Tp&, size_type, size_type, const _Alloc&) [with <template-parameter-2-2> = _Tp; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  774 |         basic_string(const _Tp& __t, size_type __pos, size_type __n,
      |         ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:774:9: note:   template argument deduction/substitution failed:
garbage.cpp:8:38: note:   candidate expects 4 arguments, 1 provided
    8 |    Real d = boost::math::log1p(Real(2));
      |                                      ^
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:751:9: note: candidate: 'template<class _InputIterator, class> constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(_InputIterator, _InputIterator, const _Alloc&) [with <template-parameter-2-2> = _InputIterator; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  751 |         basic_string(_InputIterator __beg, _InputIterator __end,
      |         ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:751:9: note:   template argument deduction/substitution failed:
garbage.cpp:8:38: note:   candidate expects 3 arguments, 1 provided
    8 |    Real d = boost::math::log1p(Real(2));
      |                                      ^
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:657:7: note: candidate: 'template<class> constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(size_type, _CharT, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  657 |       basic_string(size_type __n, _CharT __c, const _Alloc& __a = _Alloc())
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:657:7: note:   template argument deduction/substitution failed:
garbage.cpp:8:38: note:   candidate expects 3 arguments, 1 provided
    8 |    Real d = boost::math::log1p(Real(2));
      |                                      ^
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:634:7: note: candidate: 'template<class> constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  634 |       basic_string(const _CharT* __s, const _Alloc& __a = _Alloc())
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:634:7: note:   template argument deduction/substitution failed:
garbage.cpp:8:37: note:   cannot convert '2' (type 'int') to type 'const char*'
    8 |    Real d = boost::math::log1p(Real(2));
      |                                     ^
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:708:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  708 |       basic_string(basic_string&& __str, const _Alloc& __a)
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:708:7: note:   candidate expects 2 arguments, 1 provided
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:703:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  703 |       basic_string(const basic_string& __str, const _Alloc& __a)
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:703:7: note:   candidate expects 2 arguments, 1 provided
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:698:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(std::initializer_list<_Tp>, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  698 |       basic_string(initializer_list<_CharT> __l, const _Alloc& __a = _Alloc())
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:698:45: note:   no known conversion for argument 1 from 'int' to 'std::initializer_list<char>'
  698 |       basic_string(initializer_list<_CharT> __l, const _Alloc& __a = _Alloc())
      |                    ~~~~~~~~~~~~~~~~~~~~~~~~~^~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:670:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  670 |       basic_string(basic_string&& __str) noexcept
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:670:35: note:   no known conversion for argument 1 from 'int' to 'std::__cxx11::basic_string<char>&&'
  670 |       basic_string(basic_string&& __str) noexcept
      |                    ~~~~~~~~~~~~~~~^~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:612:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, size_type, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]'
  612 |       basic_string(const _CharT* __s, size_type __n,
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:612:7: note:   candidate expects 3 arguments, 1 provided
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:592:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, size_type, size_type, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]'
  592 |       basic_string(const basic_string& __str, size_type __pos,
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:592:7: note:   candidate expects 4 arguments, 1 provided
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:574:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, size_type, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]'
  574 |       basic_string(const basic_string& __str, size_type __pos,
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:574:7: note:   candidate expects 3 arguments, 1 provided
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:557:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, size_type, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>; size_type = long unsigned int]'
  557 |       basic_string(const basic_string& __str, size_type __pos,
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:557:7: note:   candidate expects 3 arguments, 1 provided
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:540:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  540 |       basic_string(const basic_string& __str)
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:540:40: note:   no known conversion for argument 1 from 'int' to 'const std::__cxx11::basic_string<char>&'
  540 |       basic_string(const basic_string& __str)
      |                    ~~~~~~~~~~~~~~~~~~~~^~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:528:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  528 |       basic_string(const _Alloc& __a) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:528:34: note:   no known conversion for argument 1 from 'int' to 'const std::allocator<char>&'
  528 |       basic_string(const _Alloc& __a) _GLIBCXX_NOEXCEPT
      |                    ~~~~~~~~~~~~~~^~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:515:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string() [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  515 |       basic_string()
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:515:7: note:   candidate expects 0 arguments, 1 provided
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:187:7: note: candidate: 'constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(__sv_wrapper, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]'
  187 |       basic_string(__sv_wrapper __svw, const _Alloc& __a)
      |       ^~~~~~~~~~~~
/opt/homebrew/Cellar/gcc/12.2.0/include/c++/12/bits/basic_string.h:187:7: note:   candidate expects 2 arguments, 1 provided

    "g++-12"   -std=c++20 -fvisibility-inlines-hidden -O0 -fno-inline -Wall -g -fvisibility=hidden  -DBOOST_ALL_NO_LIB=1 -DBOOST_TEST_NO_AUTO_LINK=1 -DBOOST_UBLAS_UNSUPPORTED_COMPILER=0  -I"." -I"../../.." -I"../include_private"  -c -o "../../../bin.v2/libs/math/test/garbage.test/gcc-12/debug/cxxstd-20-iso/link-static/threading-multi/visibility-hidden/garbage.o" "garbage.cpp"

Do you think this is worth continuing to pursue? I think that a slight increase in compile time is worth it to make our error messages significantly more palatable to the user.

mborland · 2022-11-29T16:40:26Z

@jzmaddock How do you want to proceed on this one? I grabbed the changes to log1p off your branch, and CI is green with all of the changes so far. Since the winter development cycle is much longer than the others I think it would be worth merging something close to see what the downstream side effects are on a limited number of functions.

Define C++20 concepts

a72ab6c

NAThompson reviewed Oct 16, 2022

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NAThompson reviewed Oct 16, 2022

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mborland added 4 commits October 17, 2022 09:05

Add intel _Quad type

c495bf7

[ci skip]

Add arbitrary arithmetic concepts

a4cd40f

[ci skip]

Add test on special function (beta)

b5344d5

[ci skip]

Add policy concept

7252320

[ci skip]

mborland added 9 commits October 17, 2022 13:50

Iterator concept example in statistics

046217c

Tighten definitions of built-in concepts by excluding 128 bit extensions

e9af348

Add definition for container

9a0905a

Workaround for libcpp++ partial implementation of concepts

b56de86

Add complex number support

b802b7c

Add execution policy concept

b03cbf5

Add any numerical type (int, floating, complex) concept

6bd07ec

Remove libc++ workaround

5b81a37

Define our own derived_from as std not available on all platforms

3420530

Merge branch 'concepts' of https://github.com/mborland/math into conc…

7a0ea9b

…epts

jzmaddock and others added 4 commits November 11, 2022 18:38

Update log1p for concept tests.

7fa561d

Merge remote-tracking branch 'upstream/develop' into concepts

1fb3a58

Merge remote-tracking branch 'upstream/concepts' into concepts

054214c

Change concept to allow integer promotion to double a la STL

2f889d4

mborland force-pushed the concepts branch from 8d805b4 to 2f889d4 Compare November 19, 2022 19:53

mborland marked this pull request as ready for review November 29, 2022 16:40

mborland mentioned this pull request Sep 11, 2023

C++20 Concepts cppalliance/decimal#68

Closed

mborland mentioned this pull request Nov 21, 2023

Implement concepts cppalliance/decimal#347

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Define C++20 concepts #848

Define C++20 concepts #848

mborland commented Oct 16, 2022

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mborland commented Nov 29, 2022

Define C++20 concepts #848

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Define C++20 concepts #848

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