Thread: calculator

Ok, I made a program that can get the operator and the variables, but really, I like it to be more of a real calculator. You know, where you can even more variables then just the preset of them ( the 2 vabls, and the oper. ). Anyone have a idea how this would be done? I was thinking of using strings, and using the "find" funchion, but really, I dont know how to go about it that way either. Any help would be most helpful.

Code:

#include <c:\tt.h>

using namespace std;

int main ()
  { clrscr();
    float a, b, result;
    char oper, ans;
    cout<<" 7 8 9 +\n 4 5 6 -\n 1 2 3 *\n 0 . /\n";
    do
        {
        cout<<"Enter first number, operator, second number: ";
        cin>>a>>oper>>b;
        switch (oper)
            {
            case '+':
            result=a+b;
            break;
            case '-':
            result=a-b;
            break;
            case '*':
            result=a*b;
            break;
            case '/':
            result=a/b;
            break;
            default: cout<<"Error";
        }
        cout<<"Answer = "<<result;
        cout<<"\nDo another (y/n)? ";
        cin>>ans;
    }
    while (ans=='y');
    getchar();
}

There's a whole bunch of ways to do it. You could use find, but you should probably implement PEMDAS (order of operations) and generally be able to tokenize the string. There is a FAQ entry on this actually. And it just so happens that the FAQ entry has code for a simple calculator expression parsing dealio. If you don't want it to be spoiled, you don't have to click, and then just google stuff or something, and just think about things. Break down the steps as small as possible and implement them in terms of code.

http://faq.cprogramming.com/cgi-bin/...&id=1044780608

Originally Posted by Tonto

There's a whole bunch of ways to do it. You could use find, but you should probably implement PEMDAS (order of operations) and generally be able to tokenize the string. There is a FAQ entry on this actually. And it just so happens that the FAQ entry has code for a simple calculator expression parsing dealio. If you don't want it to be spoiled, you don't have to click, and then just google stuff or something, and just think about things. Break down the steps as small as possible and implement them in terms of code.

http://faq.cprogramming.com/cgi-bin/...&id=1044780608

lol ok ^.^ ty, i'll look it up and then look at that link.

> #include <c:\tt.h>
You really shouldn't be writing your code in the root directory of your C drive.

Can I ask why O.o? Its only a .h file not really the work.

Ok I Understand how to get a string to be tokenize, but I dont understand how to really read the tokenized string. After I tokenize them, how would I go about reading left and right of the operator token? Sorry to be a bother XD I tried out that link, but still didnt get it fully.

Originally Posted by maxorator

If you want to mess with the drive root, make some partitions.

Lol, ok ok, but how do I got about reading the tokens I have made from the strings? I dont get how they are storaged really. XD Can someone make a small example? That would help more for me to understand. I get how they are Tokenzied just not storaged so I can read from then to compare then to my switch.

I'm doing a similar project, which involves postfix and infix notation and a stack, it would help to look that up if you want to simulate a calculator with precedence and all. as for tokenising then you should use an input string stream. Basically they are like output streams but for strings. You can take a whole line of input and store it into an input string stream (or is it output, I always get confused which one to use), and do a loop to output each token to whatever you use to evaluate. If you are doing it like that I would look up "infix to postfix notation", as it is easier to evaluate without doing a ton of conditional loops.