[C++] Need help in calculation of more than 2 numbers

A

I've made this Calculator which can only calculate for 2 inputs only. How should I write the program, so that, the user can give multiple inputs and the calculation is performed?

Code:

/*
Work of Ashrith Babu Rao, XII
Email:  a5hr1th.mb@gmail.com
(c) 2008
*/

#include <iostream.h>               
#include <conio.h>
#include <math.h>
int main()
{    clrscr();
      float P, R, T;
      int ch;
      float x,y;
      char ch1;
      do

     {

         clrscr();
         cout<<"CALCULATOR:\n----------\n\n";
      	cout<<"SIMPLE CALCULATIONS:\n-------------------\n1: Addition\n2:                  Subtraction\n3: Multiplication\n4: Division\n\n"<<endl;
         cout<<"SCIENTIFIC:\n----------\n5:  Power\n6:  Logarithm\n7:  Sin\n8:  Cos\n9:  Tan\n10: Sin Inverse\n11: Cos Inverse\n12: Tan Inverse\n"<<endl;
         cout<<"\nINTEREST CALCULATOR:\n-------------------\n13: Simple Interest\n14: Compound Interest\n\n";
      	cout<<"\nEnter Choice"<<endl;
         cin>>ch;

     	 	if(ch==1)
      	{  clrscr();
            cout<<"Addition\n--------\n\n";
            cout<<"Enter two numbers"<<endl;
            cin>>x>>y;
    	  		cout<<"\nAnswer: "<<(x+y);

         }
         if(ch==2)
      	{	clrscr();
            cout<<"Subtraction\n-----------\n\n";
         	cout<<"Enter two numbers"<<endl;
      		cin>>x>>y;
      		cout<<"\nAnswer: "<<(x-y);

         }
         if(ch==3)
      	{	clrscr();
            cout<<"Multiplication\n--------------\n\n";
         	cout<<"Enter two numbers"<<endl;
      		cin>>x>>y;
      		cout<<"\nAnswer: "<<(x*y);

         }
         if(ch==4)
      	{	clrscr();
            cout<<"Division\n--------\n\n";
         	cout<<"Enter two numbers"<<endl;
      		cin>>x>>y;
      		cout<<"\nAnswer: "<<(x/y);

         }
         if(ch==5)
         {  clrscr();
            cout<<"Power ** x^y **\n---------------\n\n";
         	cout<<"Enter two numbers"<<endl;
      		cin>>x>>y;
      		cout<<"\nAnswer: "<<pow(x,y);

         }
         if(ch==6)
      	{	clrscr();
            cout<<"Logarithm\n---------\n\n";
         	cout<<"Enter a number"<<endl;
      		cin>>x;
      	  	cout<<"\nAnswer: "<<log10(x);

         }
         if(ch==7)
      	{	clrscr();
            cout<<"Sine of X\n---------\n\n";
         	cout<<"Enter a value"<<endl;
      		cin>>x;
      	  	cout<<"\nAnswer: "<<asinl(x);

         }
         if(ch==8)
      	{	clrscr();
            cout<<"Cosine of X\n-----------\n\n";
         	cout<<"Enter a value"<<endl;
      		cin>>x;
      	  	cout<<"\nAnswer: "<<acosl(x);

         }
         if(ch==9)
      	{	clrscr();
            cout<<"Tangent of X\n------------\n\n";
         	cout<<"Enter a value"<<endl;
      		cin>>x;
      	  	cout<<"\nAnswer: "<<atanl(x);

         }
         if(ch==10)
      	{	clrscr();
            cout<<"Sine Inverse of X (Round off to nearest integer)\n------------------------------------------------\n\n";
         	cout<<"Enter a value"<<endl;
      		cin>>x;
      	  	cout<<"\nAnswer: "<<asin(x)*180/3.1416;

         }
         if(ch==11)
      	{	clrscr();
            cout<<"Cosine Inverse of X (Round off to nearest integer)\n--------------------------------------------------\n\n";
         	cout<<"Enter a value"<<endl;
      		cin>>x;
      	  	cout<<"\nAnswer: "<<acos(x)*180/3.1416;

         }
         if(ch==12)
      	{	clrscr();
            cout<<"Tangent Inverse of X (Round off to nearest integer)\n---------------------------------------------------\n\n";
         	cout<<"Enter a value"<<endl;
      		cin>>x;
      	  	cout<<"\nAnswer: "<<asin(x)*180/3.1416;

         }
         if(ch==13)
      	{	clrscr();
            cout<<"Simple Interest\n---------------\n\n";
            cout<<"Enter Principal Amount: ";
            cin>>P;
            cout<<"\nEnter Rate of Interest: ";
            cin>>R;
            cout<<"\nEnter Time Period in Years: ";
            cin>>T;
      	  	cout<<"Simple Interest = Rs. "<<(P*R*T)/100;

         }
         if(ch==14)
      	{	clrscr();
            cout<<"Compound Interest\n-----------------\n\n";
            cout<<"Enter Principal Amount: ";
            cin>>P;
            cout<<"\nEnter Rate of Interest: ";
            cin>>R;
            cout<<"\nEnter Time Period in Years: ";
            cin>>T;
      	  	cout<<"Compound Interest = Rs. "<<(P*pow((1+R/100),T)-P);

         }


      cout<<"\n\nEnter More?(Y/N)"<<endl;
      cin>>ch1;
      }while(ch1=='y');

      clrscr();
      cout<<"\n\nThank you for using!";
      cout<<"\n(c) Ashrith Babu Rao, 2008";
      getch();
}

And before someone asks, I use Borland C++ v5.02

covert infix expression to postfix/prefix and then evaluate postfix/prefix expression:
*scriptasylum.com/tutorials/infix_postfix/algorithms/postfix-evaluation/index.htm

lol

Create a do-while loop that ends when the user enters a particular char. eg "=".
This way,

if(ch==1)
{
clrscr();
cout << "Addition\n--------\n\n";
cout << "Enter the numbers"<<endl;
double x, sum;
do
{
cin >> x;
sum += x;
}while(x != 0.0)

cout << "\nAnswer: " << sum;

Get the user to enter a large string like "2+4+5+6-9/5*3" and parse the expression

that should be more than impressive for your school staff

^^ Pretty good technique
Had it been Java i would have used it... but since im very new to c++, i dont know how to parse and break a string.
If you could please help with the syntax??

^^lol...you have to take care of precedence and brackets too, if any

A good technique is to first convert it to prefix or postfix form and then evaluate easily using simple stack

Yaar the coding you have done looks good.. but I suggest you one thing.. (Have completed XIIth in 2007 with Computer Science :lol:

)
Advice: Instead of using so many (if.. else) controls .. use a single switch(ch1) control.. This way you will have a better organised programme to look @.
Secondly, use functions buddy.. e.g for Addition use a function named Add().
I tell you teachers really get impressed with these techniques I've told you.. worked for me! Will definitely work for you..

BTW which school r u frm??

Yep, As T159 said, the best way to evaluate is to convert it to postfix, and use a stack to evaluate it. I'm sure you would have learnt postfix and stacks at school. I remember learning that.

Here's an explaination of stacks and a simple stack implementation in C that you can use for this purpose, as instructed already by many above.

V

put to loop to read more numbers and exit the loop when last number entered is zero.
Caution: Enter the message to enter 0 to exit.

You can add subtract and multiply more than 2 numbers by this method.

[offtopic] @qwertmaniac and @t159 Do you really think that in India they teach Prefix/Postfix at school level ? [/offtopic]

@a5hr1th Use descriptive variable names dude! Its considered a good programming practice.

Anyways since in using this prefix-postfix thingy.. You can look at my code.. see if this makes any sense to you... If not, I suggest don't bother. Its not worth it.

Code:

/*
Coded By n00bish_king_of_Jellula aka Quiz_Master.
*/

#include <iostream>
#include <stack> 
#include <string>
using namespace std;

void main()
{
    int i, selection = 1;
    string postfixExp;
    char token;
    float value, value1, value2;
    stack<float> s; //Declare a stack of floats

    while (selection != 0)
    {
        cout << "1. Evaluate a postfix expression" << endl;
        cout << "0. Exit " << endl;
        cout << "Enter the number for the option: ";

        cin >> selection;
        switch(selection)
        {
            case 1: cout << "Evaluate a postfix expression\n";
                    cout << "Enter the expression: ";
                    cin >> postfixExp;
                    i = 0;
                    token = postfixExp[i];
                    while((i < postfixExp.size()) && (token != '='))
                    {
                        if(isdigit(token))
                        {
                            value = token - '0';
                            s.push(value);
                        }
                        else
                        {
                            value2 = s.top();
                            s.pop();
                            value1 = s.top();
                            s.pop();
                            switch(token)
                            {
                                case '+': value = value1 + value2;
                                          break;
                                case '-': value = value1 - value2;
                                          break;
                                case '*': value = value1*value2;
                                          break;
                                case '/': value = value1/value2;
                                          break;
                            }
                            s.push(value);
                        }
               i++;
               token = postfixExp[i];
                    }
                    value = s.top();
                    s.pop();
                    cout << postfixExp << " " << value << endl;         
                    break;

            case 0: cout << "Exiting the program\n";
                    break;

            default: cout << "Invalid option\n";
                    break;
        }
     cout << endl;
    }
}

Opps sorry.. I forgot..I am no more visiting this forum! Ignore this please! I was NOT even here... An AI spyware is impersonating me!

^^Yeah I think its in 12th class book, postfix prefix is used in stack chapter