C/C++ programming

[jonssonj]

Hello!

I wonder how I can check that a input made by a user, really is an integer and not anything else.

F.eg.

#include

using namespace std;

int main(void)
{
   int test;
   cout << "Enter integer: ";
   cin >> test;

   // Now I want to check that the user really entered an
   // integer and not anything else.
}


BR
Jörgen Jönsson

[jonssonj]

Hello all!

I use two functions that solves the problem I had.

One from MSDN that clears the cin buffer and one function that I wrote myself, that checks if the input is an integer or not.

Code: [Select]



int main(void)
{
char *buffer = 0;
buffer = new char[11];
int x=0;
int nState=0;

bool inmatning = true;

while(inmatning)
{
          // ................
          // other code goes here
          // ...................

          // I only saves 9 numbers so the biggest
          // number a user can enter is 999999999.
          cin.getline(buffer,10);
          nState = ClearError(cin);
          if(CheckForInteger(buffer))
 {
            x=atoi(buffer);
            if (x>=0)
   {
              //.................
              // other code goes here..
              //..................
            } else
               inmatning=false;
          } else
              cout << &quot;\nWrong input!&quot;;
        }
}


// Function from MSDN
int ClearError(istream& isIn)        // Clears istream object
{
    streambuf*  sbpThis;
    char        szTempBuf[20];
    int         nCount, nRet = isIn.rdstate();

    if  (nRet)                        // Any errors?
    {
        isIn.clear();                 // Clear error flags
        sbpThis = isIn.rdbuf();       // Get streambuf pointer
        nCount = sbpThis->in_avail(); // Number of characters in buffer

        while (nCount)                // Extract them to szTempBuf
        {
            if  (nCount > 20)
            {
                sbpThis->sgetn(szTempBuf, 20);
                nCount -= 20;
            }
            else
            {
                sbpThis->sgetn(szTempBuf, nCount);
                nCount = 0;
            }
        }
    }

    return  nRet;
}


// Function that checks if it's an integer or not.
bool CheckForInteger(char *input)
{
// int max = 2147483647;


// Initialize some variables.
bool heltal = true;
int length = 0;

// continue until the last char.
while(*input !='\0')
{
// if we find a '-' sign at the first pos.
// we ignore it.
if ( !(*input=='-' && length==0) )
{
// check if the current char is a
                        // digit.
if (!isdigit(*input))
{
// if not, we set the returnvalue to false.
heltal = false;
}
}
// go to next char and count allt the chars.
input++; length++;
}

// go back to first char in buffer.
input = input - length;

// return result.
return heltal;

}





Thanks for all your help and thanks for a great forum and a great community.

BR
Jörgen Jönsson

===========================================
Now I only owns one A500. I will buy a A-One when a new
model reaches the market (I'm optimistic )