How do I get the flush function to work?

[joder2006]

For this problem I know I need some kind of flush function to fix it, I have a program that runs as a calculator and everything works fine accept if I input a character the program does an infinite loop because its expecting a float, how do I get it to where the program continues on without the infinite loop, here is my code.

// Program 3
// 10/17/2006
// This program is a calculator
 
#include <iostream>
#include <cmath>
#include <string>
#include <stdio.h>
 
 
using namespace std;
 
 void instructions ()
 
// Repeated instructions for the user
{
cout << "Type your operation then the number;" << endl; 
}
 
void main ()
{
float accum, num;
char op;
op = 0;
accum = 0.0;
 
 
// Beggining instructions for the user
 
cout << "type * for multiplication;" << endl;
cout << "type / for division;" << endl;
cout << "type - for subtraction;" << endl;
cout << "type + for addition;" << endl;
cout << "type q, Q, or = to quit;" << endl;
 
// Calculator process
 
while ((op!='q')&& (op!='Q') && (op!='='))
{
instructions ();
 
cin >> op;
if (op!='q'&& op!='Q' && op!='=')
{    switch (op)
 
        // The operations for the calculator
 
        {
        case '+':
            cin >> num;
            accum = accum + num;
            cout << accum << " " << endl;
            break;
        case '-':\
            cin >> num;
            accum = accum - num;
            cout << accum << " " << endl;
            break;
        case '*':
            cin >> num;
            accum *= num;
            cout << accum << " " << endl;
            break;
        case '^':
            cin >> num;
            accum = pow(accum, num);
            cout << accum << " " << endl;
            break;
        case '/':
        cin >> num;
        if (num == 0) 
        {
            // If the user inputs zero it won't crash
 
 
                cout << "Error: You Can't divide by a '0'.";
                cout << endl << endl; accum;
        } if (num != 0)
               { 
 
 
                accum = (accum / num);
                cout << accum << " " << endl;
            }
                break;
        default:
            cout << "invalid operation" << endl;
 
} }
        if (num == '\n' && op != 'q' && op != 'Q' && op != '=')
          {cout << "Invalid input" << endl; }
             num = '\n';
 
             if (op =='q'|| op == 'Q' || op == '=')
             {cout << "Thanks for using my program " << endl;}
 
}
system("pause");
}

[arne]

For this problem I know I need some kind of flush function to fix it, I have a program that runs as a calculator and everything works fine accept if I input a character the program does an infinite loop because its expecting a float, how do I get it to where the program continues on without the infinite loop, here is my code.

// Program 3
// 10/17/2006
// This program is a calculator

#include <iostream>
#include <cmath>
#include <string>
#include <stdio.h>


using namespace std;

void instructions ()

// Repeated instructions for the user
{
cout << "Type your operation then the number;" << endl;
}

void main ()
{
float accum, num;
char op;
op = 0;
accum = 0.0;


// Beggining instructions for the user

cout << "type * for multiplication;" << endl;
cout << "type / for division;" << endl;
cout << "type - for subtraction;" << endl;
cout << "type + for addition;" << endl;
cout << "type q, Q, or = to quit;" << endl;

// Calculator process

while ((op!='q')&& (op!='Q') && (op!='='))
{
instructions ();

cin >> op;
if (op!='q'&& op!='Q' && op!='=')
{ switch (op)

// The operations for the calculator

{
case '+':
cin >> num;
accum = accum + num;
cout << accum << " " << endl;
break;
case '-':\
cin >> num;
accum = accum - num;
cout << accum << " " << endl;
break;
case '*':
cin >> num;
accum *= num;
cout << accum << " " << endl;
break;
case '^':
cin >> num;
accum = pow(accum, num);
cout << accum << " " << endl;
break;
case '/':
cin >> num;
if (num == 0)
{
// If the user inputs zero it won't crash


cout << "Error: You Can't divide by a '0'.";
cout << endl << endl; accum;
} if (num != 0)
{


accum = (accum / num);
cout << accum << " " << endl;
}
break;
default:
cout << "invalid operation" << endl;

} }
if (num == '\n' && op != 'q' && op != 'Q' && op != '=')
{cout << "Invalid input" << endl; }
num = '\n';

if (op =='q'|| op == 'Q' || op == '=')
{cout << "Thanks for using my program " << endl;}

}
system("pause");
}

cin.clear();
 

will clear your input buffer and prevent the infinite loop.

[weaknessforcats]

cin.clear() does not flush the input buffer. All it does is reset the failbit buit the offending data is still in the buffer. Use cin.ignore() to skip or cin.get() to eat it.

C++ does not own the input buffer.You may need an operating system call to flush the input buffer. Microsoft uses __flushall().

The input buffer accumulates characters until the enter key is pressed. Only then is data accessible to your program. When you reach the enter key, the program will ask for more data forever. The only way to terminate the input is to put an "end of all data" terminator in the buffer. This is a CTRL+Z. (Note: This has to be a CTRL+Z followed by an enter key)