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c++ostringstreamexpression-evaluation

Odd behavior with doubles and oStringStream

so I am working on an expression evaluator as an internal component on a work related project. but I am having some weird behavior when it comes to the output of floating point math...

the evaluator takes in a string 

e.evaluate("99989.3 + 2346.4");
//should be 102335.7
//result is 102336

//this function is what returns the result as a string
template <class TYPE> std::string Str( const TYPE & t ) {
    //at this point t is equal to 102335.7
std::ostringstream os;

os << t;
    // at this point os.str() == 102336
return os.str();

it appears almost as if any floating point number above e+004 scientific notation is being rounded to the nearest whole number. can anyone explain why this is happening and how I might overcome this issue.

Solution

  • You can set the precision with std::setprecision.

    With a bit of help from std::fixed