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Latest attempt at this loop

djru (30)
Okay i'm still working on my calculator and i'm at the last part and can't get my loop to work correctly. I need my program to receive the first number, display the operator then the operand, then allow user to input a second, third, forth, however many he wants until he quits the program by pressing q. Of course I was trying to constantly update my variable so that I could perform new operation on it. Example:
+ 5.0
result so far is 5.0
^2
result so far is 25.0
/ 2.0
result so far is 12.5
q 0
final result is 12.5

and here's the code I have so far:

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#include <iostream>
#include <math.h> 


using namespace std;

//Prototypes

//Retrieves the operator, operand and returns operator
//and operand

void scan_data(char, float);

//Reads operator and operand and uses switch statement
//to perform correct operator on the operand

double do_nex_op(char, float, float&);

//Reads result and outputs the result of the operator
//and the operand

float do_next_op(float);

int main()
{
    char op;
    float num2;
    float sum;

    
  cout<< "This program is a very basic calculator \n";
  cout<< "use only operators +,-,*,/, or ^";
  cout<<" to raise a number to a power\n\n";

    
  //display operator and operand
    
    scan_data(op, num2);

    
return 0;    

}

// function to obtain original values

void scan_data(char op, float num2)
{
 
   float num;
   float result;
  
      num = do_nex_op ( op, num2, num);
  
      result = do_next_op(num);

}

// performs operation based on operator input

double do_nex_op(char op, float num2, float& num)
{
   num = 0;
  
  cout<< "Enter a valid operator:\n";
  cin >> op;
  
  cout<< "Enter any number:\n";
  cin >> num2;
       switch (op)
        {
            case'+':
                cout << "\n+"<< num;
                num = num + num2;
                cout<<"\n\n result so far " << num;
                break;
            case '-':
                cout << "\n-"<< num2;
                num = num - num2;
                cout <<"\n\n result so far " << num;
                break;
            case '*':
                cout << "\n*"<< num2;
                num = num * num2;
                cout <<"\n\n result so far "<< num;
                break;
            case '/':
                cout << "\n/"<< num2;
                num = num / num2;
                cout <<"\n\n result so far "<< num;
                break;
            case '^':
                cout << "\n^"<< num2;
                num = pow(num, num2);
                cout <<"\n\n result so far "<< num;
                break;
            case 'q':
                cout <<"\n q" <<" 0";
                cout << "\n\n final result is"<< num;
            default:
                cout<<"\n\n Invalid operator";
                
          }
    
     
   
      
  return (num);
}
// suppose to initiate my loop but not working!!!
float do_next_op(float num)
{
    float num2;
    char op;
    while(!(num2/0))
        cout<<"Enter Next Operation:\n";
        cin>> op;
        cout<<"Enter next number: \n";
        cin>> num2;
    switch(op)
    {
            case'+':
                cout<<"\n +"<< num2;
                num= num2 + num;
                cout<< "result so far is "<< num;
                break;
            case'-':
                cout<<"\n -"<< num2;
                num= num2 - num;
                cout<<"result so far is "<< num;
                break;
            case'*':
                cout<<"\n *"<< num2;
                num= num2 * num;
                cout<<"result so far is "<< num;
                break;
            case'/':
                cout<<"\n /"<< num2;
                num= num2 *num;
                cout <<"result so far is "<< num;
                break;
            case'^':
                cout<<"\n ^"<< num2;
                num= pow(num2, num);
                break;
            case 'q':
                cout<<"\n q"<<"0";
                cout<<"Final result is: \n";
                cout<< num;
            default:
                cout<<"Not a valid operator";
    }        
                    
                    
                    
            


}

One things for sure I've at least gotten good a switch statements if nothing else.
Last edited on
TheIdeasMan (6817)
Hi djru,

First, please use the code tags - it is the <> on the right under format.

Have you used the debugger? Or put cout statements in where you think there is a problem, so you can see the values of your variables.

Let us know how you get on

TheIdeasMan
djru (30)
Thanks, that does look MUCH better, I just got off work so i am going to try what you suggested. I know its recognizing my switch statement, the problem is when i try to use a loop its not returning to enter next operation. I was tired last night so I am pretty sure I just need to play around with it some more
TheIdeasMan (6817)
You have 2 do_next_op functions that are identical. this might work in C++ because you can have function overloading with different argument types, but this is definitely the wrong way to do it here.

You need a while loop in main with a carefully chosen test-expression.
djru (30)
Okay, i guess I was just tired last night because I got the while loop to run the first try, the teacher wanted it weird like that, i think to try and trick us up but one function is do_NEX_op with no T and the other one is do_NEXT_op with a t. This is the code I ended up with
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#include <iostream>
#include <math.h> 


using namespace std;

//Prototypes

//Retrieves the operator, operand and returns operator
//and operand

void scan_data(char, double);

//Reads operator and operand and uses switch statement
//to perform correct operator on the operand

double do_nex_op(char, double, double&);

//Reads result and outputs the result of the operator
//and the operand

float do_next_op(double);

int main()
{
    char op;
    double num2;
    double sum;

    
  cout<< "This program is a very basic calculator \n";
  cout<< "use only operators +,-,*,/, or ^";
  cout<<" to raise a number to a power\n\n";

    
  //display operator and operand
    
    scan_data(op, num2);

    
return 0;    

}

// function to obtain original values

void scan_data(char op, double num2)
{
 
   double num;
   double result;
  
      num = do_nex_op ( op, num2, num);
  
      result = do_next_op(num);

}

// performs operation based on operator input

double do_nex_op(char op, double num2, double& num)
{
   num = 0;
  
  cout<< "Enter a valid operator:\n";
  cin >> op;
  
  cout<< "Enter any number:\n";
  cin >> num2;
       switch (op)
        {
            case'+':
                cout << "\n+"<< num2;
                num = num + num2;
                cout<<"\n\nresult so far " << num;
                break;
            case '-':
                cout << "\n-"<< num2;
                num = num - num2;
                cout <<"\n\nresult so far " << num;
                break;
            case '*':
                cout << "\n*"<< num2;
                num = num * num2;
                cout <<"\n\nresult so far "<< num;
                break;
            case '/':
                cout << "\n/"<< num2;
                num = num / num2;
                cout <<"\n\nresult so far "<< num;
                break;
            case '^':
                cout << "\n^"<< num2;
                num = pow(num, num2);
                cout <<"\n\nresult so far "<< num;
                break;
            case 'q':
                cout <<"\n q" <<" 0";
                cout << "\n\nfinal result is"<< num;
            default:
                cout<<"\n\nInvalid operator";
                
          }
    
     
   
      
  return (num);
}
// suppose to initiate my loop but not working!!!
float do_next_op(double num)
{
    double num2;
    char op;
    do
  {     cout<<"\n\nEnter Next Operation:\n";
        cin>> op;
        cout<<"Enter next number: \n";
        cin>> num2;
    switch(op)
    {
            case'+':
                cout<<"\n+"<< num2;
                num= num2 + num;
                cout<< "\nresult so far is "<< num;
                break;
            case'-':
                cout<<"\n -"<< num2;
                num= num2 - num;
                cout<<"\nresult so far is "<< num;
                break;
            case'*':
                cout<<"\n *"<< num2;
                num= num2 * num;
                cout<<"\nresult so far is "<< num;
                break;
            case'/':
                cout<<"\n/"<< num2;
                num= num2 / num;
                cout <<"\nresult so far is "<< num;
                break;
            case'^':
                cout<<"\n ^"<< num2;
                num= pow(num2, num);
                cout << "\nresult so far is "<< num;
                break;
            case 'q':
                cout<<"\n q"<<"0";
                cout<<"\nFinal result is: \n";
                cout<< num;
            default:
                cout<<"\nNot a valid operator";
    }        
 } while (num != 'q');             
                    
                    
   return 0;         


}


Now I am debugging and trying to figure out why when I try to use the division operator in my loop its returning a weird decimal
For example : I input 24 as my first operand, then when prompted try to divide it by 2 and it returns 0.083333333, weird, i tried to change all my floats to doubles and it didn't really do anything which is understandable if I understand the difference correctly. It was worth a try though
djru (30)
And I believe I just figured that part out I had 
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case'/':
                cout<<"\n/"<< num2;
                num= num2 / num;
                cout <<"\nresult so far is "<< num;
                break;


When I needed
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case'/':
                cout<<"\n/"<< num2;
                num= num / num2;
                cout <<"\nresult so far is "<< num;
                break;


I had my num and num2 variables reverse
djru (30)
I do have one more quick question,

Would it be bad programming to use a if/else statment inside of my switch statement.
I ask because I am trying to think of how I would display an error if the user tries to divide a number by 0
For example:
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case'/':
                  cout<<"\n/"<<num2;
                  if (num2 = 0)
                   cout<<"Error Cannot divide by zero";
                  else
                   num= num / num2;
                   cout << "\nresult so far is "<< num;
                  break;
TheIdeasMan (6817)
Don't use do while loops - they can be as confusing as hell. Use a while loop instead.

You still have 2 do_next_op functions - not good.

When using cout, don't use "\n" use endl like this 

 
 
 cout<<"\nFinal result is: " << endl;


endl flushes the buffer which can be important sometimes.

If you do division, check for divide by zero.



Edit: what happens when you step through with the debugger?
Last edited on
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