Check if "cin" is a string

Question

I have a simple little script I am coding, and I am trying to not allow people to enter a string, or if they do make it revert to the beginning of the function again. Here's the input code I have:

int main()
{
    cout << "Input your first number" << endl;
    cin >> a;
    cout << "Input your second number" << endl;
    cin >> b;
}

The rest of the code beyond this part works just fine for what's going on, although if a string is entered here it obviously doesn't work.

Any help would be appreciated.

Post working code - `a` and `b` aren't declared here. – Pubby Jan 18 '13 at 04:10 — Pubby, Jan 18 '13 at 04:10
What are the types of `a` and `b` respectively? – David G Jan 18 '13 at 04:10 — David G, Jan 18 '13 at 04:10

score 1 · Accepted Answer · edited May 23 '17 at 10:24

1

You may find this post useful,

How to check if input is numeric in C++

Basically you can check the input, whether it is numeric value or not. After checking whether the given input is numbers, then you can add a while loop in main to ask user to repeat if input is not a valid number.

edited May 23 '17 at 10:24

Community

1
1

answered Jan 18 '13 at 04:16

taocp

23,276
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fscan · Answer 2 · 2013-01-18T04:27:41.913

0

Every input is a string. If you want to know if a entered string can convert to a number, you have to read in a string and try to convert it yourself (eg with strol).

An alternative would be to check if the reading from cin failed, but personally i don't like it because cin.fail() covers more error situations than just a failed type conversion.

edited Jan 18 '13 at 04:27

answered Jan 18 '13 at 04:18

fscan

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score 0 · Answer 3 · answered Jan 18 '13 at 11:55

0

There's a library function may help,you can check it after input:

int isdigit(char c);

Tips: 1.You should include such files :

# include <ctype.h>

2.If c in 0 ~ 9 ,return 1 ; else return 0.

answered Jan 18 '13 at 11:55

KingsOfTechENG

59
3

Check if "cin" is a string

3 Answers3