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::do_assign(const Exp&, const boost::multiprecision::detail::modulus_immediates&) [with Exp = boost::multiprecision::detail::expression, et_on>, boost::multiprecision::number, 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::do_assign(const boost::multiprecision::detail::expression&, const mpl_::true_&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number, et_on>, Arg2 = boost::multiprecision::number, 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::result_type, boost::multiprecision::number >, boost::multiprecision::number&>::type boost::multiprecision::number::operator=(const boost::multiprecision::detail::expression&) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number, et_on>, Arg2 = boost::multiprecision::number, 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::number(const boost::multiprecision::detail::expression&, typename boost::enable_if_c::result_type,boost::multiprecision::number

::value, void>::type*) [with tag = boost::multiprecision::detail::modulus_immediates, Arg1 = boost::multiprecision::number, et_on>, Arg2 = boost::multiprecision::number, 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