Migrate to VS2013 Comparison operator Error C2678:binary '==' no operator

Question

I have below code works fine in visual studio 2005. But get compile errors when migrating to visual studio 2013.

// Check if the row in the file starts with a double value
bool RowReader::isDouble(std::wstring value)
{
    double testValue;
    std::wistringstream in(value);
    in.setf(std::ios::dec, std::ios::basefield);

    if((in >> testValue) == NULL)
        return false;

    return true;
}

The error is:

Error   1   error C2678: binary '==' : no operator found which takes a left-hand operand of type 'std::basic_istream<wchar_t,std::char_traits<wchar_t>>' (or there is no acceptable conversion)

Any help ? I am very new to this. 1. Is testValue initial value 0 ? 2. Why if it's equal to NULL if the first character is not double ? 3. How to fix this compile error?

Answer 1

Problem solved. See below code:

bool isDouble(std::wstring value)
{
    wchar_t * endptr = 0;
    wcstod(value.c_str(), &endptr);
    if (*endptr != '\0' || endptr == value.c_str()){
        return false;
    }
    return true;
}