c++mfcroundingc-stringsatof

C++ atof/_wtof, rounding error

I have a CString variable which I need to convert into double

CString sVal(_T("    4.2"));
double dbl2 = _wtof(sVal);

And I got dbl2 = 4.0000 instead of 4.2. What could be the reason for the rounding?

Solution

  • decimal point is one of the "items" in localization

    WARNING!!! below code is not optimized for many subsequent conversions

    #include <locale.h> 
#include <string>

...

CString sVal(_T("    4.2"));

std::string currentLocale = setlocale(LC_NUMERIC, NULL); //retrive current locale
setlocale(LC_NUMERIC, "C"); //change numeric locale to C, now decimal separator is '.'

double dbl2 = _wtof(sVal);

setlocale(LC_NUMERIC, currentLocale.c_str()); //return to original locale

    See http://www.cplusplus.com/reference/clocale/setlocale/