problem with my semple calculator

ringawy (2)
hello all i'm write simple calculator and i have some problem at verfiy the input and using functions and need some advice to make the code better
at this code if user input bad char at operathion the program crash how i can solve it ?
and how i can use cin.ignore and cin.clear any one can explains all kind of cin


the code 

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/*
  Name: mohamed elhababshe
  Copyright: rinGawy Team
  Author: mohamed elhabashe
  Date: 24/01/12 02:27
  Description: simpel calculator
*/

#include <cstdlib>
#include <iostream>
float a,b;
int e,f,c;

using namespace std;
void Errorinput(void)
{
cout<<"-------------------------"<<endl<<"Error Enter your number again"<<endl<<"-------------------------"<<endl;
}

void Errormethod(void)
{
cout<<"-------------------------"<<endl<<"Error "<<a<<"/0 Wrong method cannot divide by zero please correct your method"<<endl<<"-------------------------"<<endl;
}

void Erroroperathion(void)
{
cout<<"-------------------------"<<endl<<"Error please Enter your operathion again"<<endl<<"-------------------------"<<endl;
}

int main()
{
    char d;
    do{
         first:
    cout<<"hello this main menu please Enter your choice number"<<endl<<"1-Enter calculating program"<<endl<<"2-information about me"<<endl<<"3-no thanks get me out of here"<<endl<<"=>>";
    cin>>c;
    if(cin.fail()==true)
    {
    cin.clear();
    cin.ignore(1);
    Errorinput();
    goto first;
    }
    else
    switch(c)
    {
             case 1:{
                  cout<<"welcome to my simple calculator"<<endl<<"Enter frist number =";
                  cin>>a;
                  if(cin.fail()==true)
                  {
                  cin.clear();
                  cin.ignore(1);
                  Errorinput();
                  goto first;
                  }
                  else
                  cout<<"Enter second number =";
                  cin>>b;
                  if(cin.fail()==true)
                  {
                  cin.clear();
                  cin.ignore(1);
                  Errorinput();
                  goto first;
                  }
                  else
                  cout<<"Enter your arithmetic operathion like ( + , - , * , / ,% ) =";
                  cin>>d;
                  if(cin.fail()==true)
                  {
                  cin.clear();
                  cin.ignore (10);
                  Erroroperathion();
                  goto first;
                  }
                  else
                      
                      switch(d)
                      {
                      case '+':cout<<"------------------"<<endl<<a<<"+"<<b<<"="<<a+b<<endl<<"------------------"<<endl;break;
                      case '-':cout<<"------------------"<<endl<<a<<"-"<<b<<"="<<a-b<<endl<<"------------------"<<endl;break;
                      case '*':cout<<"------------------"<<endl<<a<<"*"<<b<<"="<<a*b<<endl<<"------------------"<<endl;break;
                      case '/':{
                           if(b==0)
                           {
                                  Errormethod();
                                  goto first;
                           }
                           else
                           cout<<"------------------"<<endl<<a<<"/"<<b<<"="<<a/b<<endl<<"------------------"<<endl;break;
                           }
                      case '%':{
                           if(b==0)
                           {
                                  Errormethod();
                                  goto first;
                           }
                           else
                           e=(int)a;
                           f=(int)b;
                           cout<<"------------------"<<endl<<e<<"%"<<f<<"="<<e%f<<endl<<"------------------"<<endl;break;
                               }
                      default:Erroroperathion();
                      }
                      };break;
               case 2:cout<<"---------------------------------"<<endl<<"my name: mohamed elhabashe"<<endl<<"my age: 25"<<endl<<"from: Egypt (country of fredoom)"<<endl<<"---------------------------------"<<endl;break;
               case 3:cout<<"bye bye see you later"<<endl;break;
               default:{
                  Errorinput();
                  goto first;
                  };
               }        
}while(c!=3);
    system("PAUSE");
    return 0;
}


Texan40 (645)
cin::ignore() extracts characters from the input buffer and simply discards them. If there are more characters in the buffer than you supply with the argument then they will stay in the buffer. Try using this instead:

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// need to #include <limits>
cin.ignore(std::numeric_limits<int>::max(),'\n');
cin.clear();


This should suffice for clearing out the input stream.
Vortex47 (11)
Just out of curiosity, is there any reason for why you made classes for the error messages or is it to make it cleaner?
ringawy (2)
Texan40 thx for help i will try your instead and comment back

Vortex47 thx for help yea i'm using classes to make it cleaner and if i need chinge any message wiil be easy for all program and i'm want develop this project more and more

be back



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