When I use getline
, I would input a bunch of strings or numbers, but I only want the while loop to output the "word" if it is not a number.
So is there any way to check if "word" is a number or not? I know I could use atoi()
for
C-strings but how about for strings of the string class?
int main () {
stringstream ss (stringstream::in | stringstream::out);
string word;
string str;
getline(cin,str);
ss<<str;
while(ss>>word)
{
//if( )
cout<<word<<endl;
}
}
Another version...
Use strtol
, wrapping it inside a simple function to hide its complexity :
inline bool isInteger(const std::string & s)
{
if(s.empty() || ((!isdigit(s[0])) && (s[0] != '-') && (s[0] != '+'))) return false;
char * p;
strtol(s.c_str(), &p, 10);
return (*p == 0);
}
strtol
?As far as I love C++, sometimes the C API is the best answer as far as I am concerned:
strtol
seems quite raw at first glance, so an explanation will make the code simpler to read :
strtol
will parse the string, stopping at the first character that cannot be considered part of an integer. If you provide p
(as I did above), it sets p
right at this first non-integer character.
My reasoning is that if p
is not set to the end of the string (the 0 character), then there is a non-integer character in the string s
, meaning s
is not a correct integer.
The first tests are there to eliminate corner cases (leading spaces, empty string, etc.).
This function should be, of course, customized to your needs (are leading spaces an error? etc.).
See the description of strtol
at: http://en.cppreference.com/w/cpp/string/byte/strtol.
See, too, the description of strtol
's sister functions (strtod
, strtoul
, etc.).