id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
9579,conversion error from boost cpp_rational to int,W Randolph Franklin <boost@…>,John Maddock,"boost cpp_rational seems to convert wrong to int when the numerator and denominator have many digits.
{{{
 #include <iostream>  #include <boost/multiprecision/cpp_int.hpp>

 using namespace boost::multiprecision;
 using namespace std;

 int main() {
  cpp_rational a(""4561231231235/123123123123"");
  std::cout << ""bad convert: "" << a << ' '  << 
     float(a) << ' ' << int(a) << ' ' << 
     a.convert_to<int>() << endl;
  a = (cpp_rational)""456/123"";
  std::cout << ""good convert: "" << a << ' '  <<
     float(a) << ' ' << int(a) << ' ' << 
     a.convert_to<int>() << endl;
 }
}}}
The output is:
{{{
 bad convert: 651604461605/17589017589 37.0461 -3 -3
 good convert: 152/41 3.70732 3 3
}}}
Also, attempts to convert cpp_rational to cpp_int fail to compile, e.g., using
{{{
 cpp_int b = static_cast<cpp_int> (a);
 cpp_int b = a.convert_to<cpp_int>();
}}}
What I want to happen is to divide and round down and never get it wrong even close to an int.

Help? Thanks.
",Bugs,closed,To Be Determined,multiprecision,Boost 1.55.0,Problem,fixed,cpp_rational conversion,