integer validation

[Violet_82]

Hi all,
I am trying to make sure that users can only input integers in my program and no other types. Here is the program:

#include<iostream>

using namespace std;

int main()
{

int numbers[9];
int k;

cout<<"Enter 9 numbers: ";

for( k = 0; k<9; k++)
{
cin >> numbers[k];
}
cout<<"here are your numbers: ";
for (k=0; k<9; k++)
{
cout<<" "<<numbers[k];
}

}

I am having real trouble (I am still a beginner) to validate user input.
I have tried with the

isdigit()

function, with if

((numbers[k]<'48' || numbers[k]>'58'))

because I thought that the ascii table would have been of use but no joy. All the above included in a while loop of course...

I meant I tried things like:

while((numbers[k]<'48' || numbers[k]>'58'))
	{
		cout<<"wrong, again ";
			cin >> numbers[k];
	}

or

while((!isdigit(numbers[k]))
	{
		cout<<"wrong, again ";
			cin >> numbers[k];
	}

Any suggestion?
thanks

[Ancient Dragon]

The easoest way to validate that all input only contains digits it to get the input as a string instead of an integer. Then you can easily determine if it contains any non-digit characters without screwing up the entire input stream.

>>while((!isdigit(numbers[k]))
Useless loop because numbers can not hold anything other than digits. And cin will not let you enter anything other than digits in numeric variables.

[Violet_82]

hi ya,
thanks.
DO you mean something like

#include<iostream>

 
using namespace std;
 
int main()
{
 
char numbers[5];
int k;
 
cout<<"Enter 5 numbers: ";
 
for( k = 0; k<5; k++)
{
cin >> numbers[k];
while((numbers[k]<46) || (numbers[k]>58))
	{
		cout<<"wrong, again ";
		cin >> numbers[k];
	}
}
cout<<"here are your numbers: ";
for (k=0; k<9; k++)
{
cout<<" "<<numbers[k];
}
 
}

[Ancient Dragon]

I mean something like this:

int main()
{
   std::string number;
   cout << "Enter 5 digits\n";
   cin >> number;
   for(int i = 0; i < number.length(); i++)
   {
     if( !isdigit(number[i]) )
     {
        cout << "You idot!  Numeric digits only!;
        break;
     }
   }
}

[Violet_82]

oh I see, it makes sense yes thanks. But what if I want to keep the int array? Do you think i could do that and maybe use a cast construct? Or is it not an option?

[Ancient Dragon]

After the validation you cn convert the string to an integer if you want to.

#include <sstring>
...
<snip>
int n;
stringstream s;
s << number;
s >> n;
cou << n << '\n';

Unless you are instructed to do so there is no reason to put each digit of the string in its own int variable. But you could do that too

int n[5];
for(int i = 0; i < number.length(); i++)
   n[i] = number[i] - '0'; // convert ascii digit to binary

[Violet_82]

I see, thanks for your help