[Boost-bugs] [Boost C++ Libraries] #11764: boost/multiprecision/number.hpp:52:17: error: no viable overloaded '='

Subject: [Boost-bugs] [Boost C++ Libraries] #11764: boost/multiprecision/number.hpp:52:17: error: no viable overloaded '='
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-10-27 17:13:46

#11764: boost/multiprecision/number.hpp:52:17: error: no viable overloaded '='
-------------------------------------------+----------------------------
 Reporter:  Jeff Hammond <jeff.science@…>  |      Owner:  johnmaddock
     Type:  Bugs                           |     Status:  new
Milestone:  To Be Determined               |  Component:  multiprecision
  Version:  Boost 1.58.0                   |   Severity:  Problem
 Keywords:                                 |
-------------------------------------------+----------------------------
 = Summary =

 The following simple program attempts to make use of simple features in
 Boost Multiprecision and Math.  I have no problem using
 {{{constants::pi}}} with double, extended double, quad precision, or even
 a user-defined version of double double precision.  However, when I try to
 get a single precision version of this constant, it fails.

 = Source Code =

 {{{
 #include <iostream>
 #include <utility>

 #include <boost/math/constants/constants.hpp>
 #include <boost/multiprecision/cpp_bin_float.hpp>

 using boost::multiprecision::cpp_bin_float_single;
 using boost::multiprecision::cpp_bin_float_double;

 typedef boost::multiprecision::cpp_bin_float_single f32;
 typedef boost::multiprecision::cpp_bin_float_double f64;

 int main(void)
 {
 #if BUGTEST_PRECISION == 32
     //f32 pi32 = boost::math::constants::pi<f32,
 boost::math::policies::policy<boost::math::policies::digits2<32> > >();
     f32 pi32 = boost::math::constants::pi<f32>();
     std::cout << pi32 << std::endl;
 #elif BUGTEST_PRECISION == 64
     //f64 pi64 = boost::math::constants::pi<f64,
 boost::math::policies::policy<boost::math::policies::digits2<64> > >();
     f64 pi64 = boost::math::constants::pi<f64>();
     std::cout << pi64 << std::endl;
 #else
 #error Set BUGTEST_PRECISION to 32 or 64.
 #endif
     return 0;
 }
 }}}

 = Compilers Tested =

 Mac Yosemite (10.10.5):
 * Apple LLVM version 7.0.0 ({{{clang++}}})
 * Clang 3.6.2 from Homebrew
 * GCC 4.2.1 ({g++})
 * GCC 5.2.0 from Homebrew
 * Intel 16.0.0

 = Representative Output =

 Clang and GCC show nearly identical errors.  The Intel one is much shorter
 but seemingly equivalent.

 {{{
 jrhammon-mac01:boost jrhammon$ clang++ -g -Wall -std=c++11 -stdlib=libc++
 -DBUGTEST_PRECISION=64 bug.cc -o bug.x
 jrhammon-mac01:boost jrhammon$ clang++ -g -Wall -std=c++11 -stdlib=libc++
 -DBUGTEST_PRECISION=32 bug.cc -o bug.x
 In file included from bug.cc:5:
 In file included from
 /usr/local/include/boost/multiprecision/cpp_bin_float.hpp:9:
 In file included from
 /usr/local/include/boost/multiprecision/cpp_int.hpp:12:
 /usr/local/include/boost/multiprecision/number.hpp:52:17: error: no viable
 overloaded '='
       m_backend = canonical_value(v);
       ~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~
 /usr/local/include/boost/math/constants/constants.hpp:289:3: note: in
 instantiation of function template specialization
 'boost::multiprecision::number<boost::multiprecision::backends::cpp_bin_float<24,
       boost::multiprecision::backends::digit_base_type::digit_base_2,
 void, short, -126, 127>,
 boost::multiprecision::expression_template_option::et_off>::number<float>'
 requested here
   BOOST_DEFINE_MATH_CONSTANT(pi,
 3.141592653589793238462643383279502884e+00,
 "3.141592653589793238462643383279502884197169...
   ^
 /usr/local/include/boost/math/constants/constants.hpp:246:13: note:
 expanded from macro 'BOOST_DEFINE_MATH_CONSTANT'
    { return BOOST_JOIN(x, F); }\
             ^
 /usr/local/include/boost/config/suffix.hpp:544:28: note: expanded from
 macro 'BOOST_JOIN'
 #define BOOST_JOIN( X, Y ) BOOST_DO_JOIN( X, Y )
                            ^
 /usr/local/include/boost/config/suffix.hpp:545:31: note: expanded from
 macro 'BOOST_DO_JOIN'
 #define BOOST_DO_JOIN( X, Y ) BOOST_DO_JOIN2(X,Y)
                               ^
 /usr/local/include/boost/config/suffix.hpp:546:32: note: expanded from
 macro 'BOOST_DO_JOIN2'
 #define BOOST_DO_JOIN2( X, Y ) X##Y
                                ^
 <scratch space>:14:1: note: expanded from here
 3.141592653589793238462643383279502884e+00F
 ^
 /usr/local/include/boost/multiprecision/cpp_bin_float.hpp:107:19: note:
 candidate function not viable: no known conversion from
       'typename boost::disable_if<is_same<typename
 detail::canonical<float, cpp_bin_float<24,
       boost::multiprecision::backends::digit_base_type::digit_base_2,
 void, short, -126, 127> >::type, float>, typename
       detail::canonical<float, cpp_bin_float<24,
 boost::multiprecision::backends::digit_base_type::digit_base_2, void,
 short,
       -126, 127> >::type>::type' (aka 'double') to 'const
 boost::multiprecision::backends::cpp_bin_float<24,
       boost::multiprecision::backends::digit_base_type::digit_base_2,
 void, short, -126, 127>' for 1st argument
    cpp_bin_float& operator=(const cpp_bin_float &o)
 BOOST_NOEXCEPT_IF(noexcept(std::declval<rep_type&>() = std::declval<co...
                   ^
 /usr/local/include/boost/multiprecision/cpp_bin_float.hpp:303:19: note:
 candidate function not viable: no known conversion from
       'typename boost::disable_if<is_same<typename
 detail::canonical<float, cpp_bin_float<24,
       boost::multiprecision::backends::digit_base_type::digit_base_2,
 void, short, -126, 127> >::type, float>, typename
       detail::canonical<float, cpp_bin_float<24,
 boost::multiprecision::backends::digit_base_type::digit_base_2, void,
 short,
       -126, 127> >::type>::type' (aka 'double') to 'const char *' for 1st
 argument
    cpp_bin_float& operator=(const char *s);
                   ^
 /usr/local/include/boost/multiprecision/cpp_bin_float.hpp:116:19: note:
 candidate template ignored: could not match
       'cpp_bin_float<Digits, DigitBase, type-parameter-0-2, type-
 parameter-0-3, MinExponent, MaxExponent>' against 'double'
    cpp_bin_float& operator=(const cpp_bin_float<D, B, A, E, MinE, MaxE>
 &o)
                   ^
 /usr/local/include/boost/multiprecision/cpp_bin_float.hpp:129:74: note:
 candidate template ignored: substitution failure
       [with Float = double]: no type named 'type' in
 'boost::enable_if_c<false,
 boost::multiprecision::backends::cpp_bin_float<24,
       boost::multiprecision::backends::digit_base_type::digit_base_2,
 void, short, -126, 127> &>'
       && (std::numeric_limits<Float>::radix == 2), cpp_bin_float&>::type
 operator=(const Float& f)
                                                                     ~~~~ ^
 /usr/local/include/boost/multiprecision/cpp_bin_float.hpp:271:30: note:
 candidate template ignored: disabled by 'enable_if'
       [with I = double]
    typename boost::enable_if<is_integral<I>, cpp_bin_float&>::type
 operator=(const I& i)
                              ^
 1 error generated.
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11764>
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