strtod how to check if 0 is error or good value

Question

I would like to to convert string to double. I do that this way:

bool String2ValueType(const std::string & a_str_value_type, double & a_result)
{
    if(a_str_value_type.empty())
        return false;

    char * end;
    double result = strtod(a_str_value_type.c_str(), &end);
    if(*end!=NULL)
        return false;
    a_result = result;
    return true;
}

How can I check if result is fine, or not, if it's value is 0? for example i will get 0 if I will send string("0"), and this is not error. But I can also send some other string- that is number, but it will not be converted and I will get also 0 (error), ( I'm talking about case when *end == 0 ).

Personally I'd use [`std::stod`](http://en.cppreference.com/w/cpp/string/basic_string/stof) instead. Regardless, if no conversion can be performed `end` is set to the initial address provided for the conversion. I.e. `end == a_str_value_type.c_str()` means no conversion took place. — WhozCraig, Jun 29 '15 at 09:36

score 4 · Answer 1 · answered Jun 29 '15 at 09:39

4

If no conversion is performed, zero is returned and the value of nptr is stored in the location referenced by endptr.

At least, that's what man page says.

answered Jun 29 '15 at 09:39

Igor S.K.

999
6
17

I do not know why but all the times I've red nullptr instead of nptr. it explains a lot, thanks – Jun 29 '15 at 11:45

strtod how to check if 0 is error or good value

1 Answers1