C++ checking if a string index is a digit

Question

#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
using namespace std;


int main()
{
    string str, temp;

    cout << "enter string: \n";
    getline (cin, str);
    vector<int> vec;
    int num;
    cout << "str size is " << str.size() <<endl;

    for (int j=0; j < str.size(); j++)
{
    int num2= str.size()-1;

    if (isdigit(str[j]))
    {
        temp+= str[j];
        num = atoi(temp.c_str());
        if (num2 ==j)
            vec.push_back(num);
    }
    else if (str[j] == ',')
    {
        num = atoi(temp.c_str());
        temp.clear();
        vec.push_back(num);

    }
    else
    {
        cout << "error\n";
        temp.clear();
    }

}
    for (int k=0; k < vec.size(); k++)
        cout << vec[k] <<endl;
}

I'm trying to make a program to where it reads in a string such as

5,6,7,8,11,120

and it'll separate the numbers from the commas, but if anything else is in the string it'll report it as an error. For example, if it was 5,6,f or 5, ,3 (space).

My program is not working though and I think it has something to do with when I am checking if it's a digit with the (isdigit) function. as it is counting fs, sds, xdx as a digit. Any idea how I can fix this?

EDIT: I've updated my code but I am still coming across problems. If I type in for example: 3,2,f it's saying that f is 0. How can I fix this?

http://stackoverflow.com/questions/4917265/can-i-tell-if-a-stdstring-represents-a-number-using-stringstream — Ben, Mar 26 '14 at 15:03
You have two seperate problems: 1) splitting a string at comma 2) checking if a string is a number. Make sure you split the problems and in your code. The first one is usually called tokenizing, the second one Bens link solves. — dutt, Mar 26 '14 at 15:06
That code seems to work as-is on ideone.com. Exactly what input are you having problems with? — molbdnilo, Mar 26 '14 at 15:10

score 1 · Answer 1 · edited Mar 26 '14 at 16:13

1

Use

std::getline(std::cin, str);

instead of

cin >> str;

Your string is getting tokenized to just the first "word". getline() reads in the whole line into str.

edited Mar 26 '14 at 16:13

ugo

2,705
2
30
34

answered Mar 26 '14 at 15:43

Farnsworth

31
3

I've updated the program but I am still coming across an issue. Can you check it out? – Mdjon26 Mar 26 '14 at 16:03

score 0 · Answer 2 · answered Mar 26 '14 at 15:18

Run the program in debug, and set a breakpoint at

cout << "error\n";

If it doesn't halt there for non-digit input, your compiler is buggy.
Your program, as far as I can tell, isn't. (apart from that it doesn't capture the last element, unless you terminate the input with ',')

Also check that you don't include any third-party header that redefines isdigit

score 0 · Answer 3 · answered Mar 26 '14 at 15:34

0

Use STL function instead C-style function. Look at http://www.cplusplus.com/reference/string/stod/

answered Mar 26 '14 at 15:34

Mayhem50

165
2
8

C++ checking if a string index is a digit

3 Answers3