Thread: Check for an integer, fail if anything else

I'm working on an integration program, that works out the integation by approximating with the rectangle rule.

I am trying to ask how many strips do you want? This MUST be an integer, yet if i enter a float, it will work. Is there a way of checking? i have looked but it seems that this integer check business is not as simple a check as it could be.

just need some code that will say

Code:

********* code*********

cout << "Please enter the number of strips:  ";
cin >> n; 

is n an integer?

       no - please retry

yes, carry on........

*********code*********

sorry, n is an integer.

Code:

#include<iostream>
using namespace std;
main()
{
float  c;
int d;

retry:
cout<<"enter a number"; 
cin>>c;
cout<<"\n";
d=c;
if((d-c)!=0)goto retry;



printf("%f",c);
}

this goes on and on until the user inputs and integer.

slymaelstrom: yes, but for some reason it wouldn't work when i entered a float.

no idea why. prob me!!

but it worked for when i entered a character, just not a float, and it needs to be a float.

QUOTED BY SLYMAELSTORM
>...and please don't listen to qqqqxxxx. goto is not the best way to do anything.

hmmmm

ok, this is what i have. apologies for incorect formatting, i'm new to this. i'm having to go out in a few minutes so i won't reply for a while either.

Code:

#include <iostream.h>
#include <iomanip.h>
#include <cmath.h>
#include <fstream.h>
#include <limits.h>
#include <stdio.h>
#include <conio.h>

float funcj(float);

int main()
{
    int n, i, m;
    float a, b, h, x, s, integral;
                            
    

    clrscr();
    cout << "************************************************************************\n\n";
    textcolor (12);
    cprintf ("The function you are integrating is x^2 - 5x - 3");

    cout << "\n\nWould you like to input your values?\n";
    cout << "OR would you like to input the values from the file rectangle.dat?";

    cout << "\n\nOption 1: Input the values\n";
    cout << "\nOption 2: Read the values\n";

    cout << "\n\nPlease enter your choice, 1 or 2:  ";
    cin >> m;

        if (m == 1)

        {

    cout << "\n\nPlease input a, the lower bound:  ";

    
    while(!(cin >> a))

        {

        textcolor (2);
        cprintf ("You have inputted the data incorrectly.");
        cout << "\nPlease try again.  ";
        return 0;
        }
      

    cout << "\nPlease input b, the upper bound:  ";

    //cin >> b;

    while(!(cin >> b ))

        {

        textcolor (2);
        cprintf ("You have inputted the data incorrectly.");
        cout << "\nPlease try again. ";
        return 0;
        
	}
    
    cout << "Please enter the number of strips:  ";
	
    while(!(cin >> n))     // If the stream fails from bad input
	
	{
   	
	cin.clear();             // Clear the fail state
   	cin.ignore(std::numeric_limits<streamsize>::max(), '\n');   // Clear the buffer
   	cout << "Invalid statement, please re-enter: ";     // Reprompt
	
	}


         }

      else if (m == 2)

         {

         ifstream read ("rectangle.dat");

         read >> a >> b >> n;
         
         }

	else 

	{ 
                textcolor (2);
                cprintf ("You have inputted data incorrectly.");
                cout << "\nPlease try again.";
                return 0;
	}

    if (a >= b)

    {
       textcolor (2);
       cprintf ("\nYou have entered the data incorrectly.");
       cout << "\na must be lower than b.\n";
       cout << "Please Try Again.\n";

    }

   // else if ( n < 1)

   //    {
   //    textcolor (2);
   //    cprintf ("\nYou have entered the data incorrectly.");
   //    cout << "\nYou must have a positive (integer) number of strips.\n";
   //    cout << "Please try again.";


   //    }

     else

    {
        integral = 0;

                                                                      
            h = fabs(a - b) / n;
        
            for  (i = 0; i < n; i++ )

            {
                                                        
                x = a + i * h;
        
                s = h * funcj(x);
                                                        
                integral = integral + s;
        
                       

            }

          textcolor (4);

          cprintf ("\nThe answer is: ");
          cout << integral << "\n";
     }
    
    return 0;
                                         
}          

float funcj(float x)
{
    float f;

    f = (x*x) - (5*x) - 3 ;

    return f;
}

i'm aware i haven't used the std that you have, so i will alter it if you need me too when i get back.

its not the finished article by any means. if you do run the program, if u use option 2, you'll need a file called rectangle.dat

which just contains 3 numbers.

Code:

2 5 100

// where a =2, b = 5, n = 100]

this just shows how i can read data from a file. its not needed but i'm just showing my teacher i can read data from a file as well as from inputting the data in the prog.

its by no means finished, but if i can just check for n being an integer, then i can then tweak it, so its more user friendly.

thanks for the help. its much appreciated.

sorry for the rushed messgae.

Originally Posted by qqqqxxxx

Code:

#include<iostream>
using namespace std;
main()
{
float  c;
int d;

retry:
cout<<"enter a number"; 
cin>>c;
cout<<"\n";
d=c;
if((d-c)!=0)goto retry;



printf("%f",c);
}

this goes on and on until the user inputs and integer.

Please stop trying to screw with people.

double post

HOMEYG
cut the crap,come up with some code first.
and the goto can be easily replaced by a while loop,but i suppose you r just lacking in talent.