Cpp_int and cpp_dec_float conversion
Hello, is there a way to convert from cpp_int to cpp_dec_float and viceversa? Since I've to use the modulus between two cpp_dec_float which I know they're integers but I need sqrt before and trying to run % with them gives: /usr/local/include/boost/multiprecision/number.hpp: In member function
‘void boost::multiprecision::number<Backend, ExpressionTemplates>::do_assign(const Exp&, const boost::multiprecision::detail::modulus_immediates&) [with Exp = boost::multiprecision::detail::expression<boost::multiprecision::detail::modulus_immediates, boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, void, void>, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’: /usr/local/include/boost/multiprecision/number.hpp:680: instantiated from ‘void boost::multiprecision::number<Backend, ExpressionTemplates>::do_assign(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&, const mpl_::true_&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’ /usr/local/include/boost/multiprecision/number.hpp:134: instantiated from ‘typename boost::enable_if<boost::is_convertible<typename boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>::result_type, boost::multiprecision::number<Backend, ExpressionTemplates> >, boost::multiprecision::number<Backend, ExpressionTemplates>&>::type boost::multiprecision::number<Backend, ExpressionTemplates>::operator=(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’ /usr/local/include/boost/multiprecision/number.hpp:181: instantiated from ‘boost::multiprecision::number<Backend, ExpressionTemplates>::number(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&, typename boost::enable_if_c<boost::is_convertible<typename boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>::result_type,boost::multiprecision::number<Backend, ExpressionTemplates> >::value, void>::type*) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’ test.cpp:20: instantiated from here /usr/local/include/boost/multiprecision/number.hpp:912: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE<false>’
Thanks in advance Best Regards
From: Boost-users [mailto:boost-users-bounces@lists.boost.org] On Behalf Of Alessandro Tagliapietra Sent: Monday, April 22, 2013 5:19 PM To: boost-users@lists.boost.org Subject: [Boost-users] Cpp_int and cpp_dec_float conversion Hello, is there a way to convert from cpp_int to cpp_dec_float and viceversa? Since I've to use the modulus between two cpp_dec_float which I know they're integers but I need sqrt before and trying to run % with them gives: /usr/local/include/boost/multiprecision/number.hpp: In member function 'void boost::multiprecision::number<Backend, ExpressionTemplates>::do_assign(const Exp&, const boost::multiprecision::detail::modulus_immediates&) [with Exp = boost::multiprecision::detail::expression<boost::multiprecision::detail::modulus_immediates, boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, void, void>, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]': /usr/local/include/boost/multiprecision/number.hpp:680: instantiated from 'void boost::multiprecision::number<Backend, ExpressionTemplates>::do_assign(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&, const mpl_::true_&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]' /usr/local/include/boost/multiprecision/number.hpp:134: instantiated from 'typename boost::enable_if<boost::is_convertible<typename boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>::result_type, boost::multiprecision::number<Backend, ExpressionTemplates> >, boost::multiprecision::number<Backend, ExpressionTemplates>&>::type boost::multiprecision::number<Backend, ExpressionTemplates>::operator=(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]' /usr/local/include/boost/multiprecision/number.hpp:181: instantiated from 'boost::multiprecision::number<Backend, ExpressionTemplates>::number(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&, typename boost::enable_if_c<boost::is_convertible<typename boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>::result_type,boost::multiprecision::number<Backend, ExpressionTemplates>
::value, void>::type*) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]' test.cpp:20: instantiated from here /usr/local/include/boost/multiprecision/number.hpp:912: error: invalid application of 'sizeof' to incomplete type 'boost::STATIC_ASSERTION_FAILURE<false>'
I'm sure John Maddock will give a fully informed reply to this, but this boost::multiprecision::expression_template_option ExpressionTemplates = et_on suggests that you might try setting the 'use expression templates' template parameter to NOT use ET boost::multiprecision::expression_template_option ExpressionTemplates = et_off HTH Paul --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow@hetp.u-net.com
is there a way to convert from cpp_int to cpp_dec_float and viceversa?
Since I've to use the modulus between two cpp_dec_float which I know they're integers but I need sqrt before and trying to run % with them gives:
You could use fmod in place of the % operator? There is an explicit conversion from cpp_int to cpp_dec_float, but no conversion in the opposite direction (in general it's unsafe). I guess we should try and figure out a generic way to implement the equivalent of iround/itrunc for that. /usr/local/include/boost/multiprecision/number.hpp: In member function
‘void boost::multiprecision::number<Backend, ExpressionTemplates>::do_assign(const Exp&, const boost::multiprecision::detail::modulus_immediates&) [with Exp = boost::multiprecision::detail::expression<boost::multiprecision::detail::modulus_immediates, boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, void, void>, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’: /usr/local/include/boost/multiprecision/number.hpp:680: instantiated from ‘void boost::multiprecision::number<Backend, ExpressionTemplates>::do_assign(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&, const mpl_::true_&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’ /usr/local/include/boost/multiprecision/number.hpp:134: instantiated from ‘typename boost::enable_if<boost::is_convertible<typename boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>::result_type, boost::multiprecision::number<Backend, ExpressionTemplates> >, boost::multiprecision::number<Backend, ExpressionTemplates>&>::type boost::multiprecision::number<Backend, ExpressionTemplates>::operator=(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’ /usr/local/include/boost/multiprecision/number.hpp:181: instantiated from ‘boost::multiprecision::number<Backend, ExpressionTemplates>::number(const boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>&, typename boost::enable_if_c<boost::is_convertible<typename boost::multiprecision::detail::expression<tag, Arg1, Arg2, Arg3, Arg4>::result_type,boost::multiprecision::number<Backend, ExpressionTemplates> >::value, void>::type*) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg2 = boost::multiprecision::number<boost::multiprecision::backends::cpp_dec_float<100u, int, void>, et_on>, Arg3 = void, Arg4 = void, Backend = boost::multiprecision::backends::cpp_dec_float<100u, int, void>, boost::multiprecision::expression_template_option ExpressionTemplates = et_on]’ test.cpp:20: instantiated from here /usr/local/include/boost/multiprecision/number.hpp:912: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE<false>’
Uh. That's a horrible message :-( I'll see if there's a way to make that any better. Regards, John.
There is an explicit conversion from cpp_int to cpp_dec_float, but no conversion in the opposite direction (in general it's unsafe).
Forgot to say: if you really must convert from cpp_dec_lfoat to cpp_int you could do: cpp_int i(my_big_float.str(0, std::ios_base::fixed)); Just make sure the float really is an integer first (use ceil/floor/trunc/round if necessary) otherwise the conversion will fail. HTH, John.
participants (3)
-
Alessandro Tagliapietra -
John Maddock -
Paul A. Bristow