25 Jan 2012 [ 201 week3 ]

On Tuesday, we (mostly) finished the simple calculator example that we started in week 2.

Here's one version we came up with that allows unlimited precision integer arithmetic:

import java.math.BigInteger;
import java.util.Scanner;

public class Calc {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        String prompt = "> ";
        System.out.print(prompt);
        while (input.hasNext()) {
            if (input.hasNext("quit")) {
                break;
            }
            BigInteger x = input.nextBigInteger();
            String operator = input.next();
            BigInteger y = input.nextBigInteger();
            BigInteger result = BigInteger.ZERO;
            if (operator.equals("+")) {
                 result = x.add(y);
            } else if (operator.equals("*")) {
                result = x.multiply(y);
            } else if (operator.equals("/")) {
                result = x.divide(y);
            } else if (operator.equals("-")) {
                result = x.subtract(y);
            } else if (operator.equals("**")) {
                int yint = y.intValue();
                result = x.pow(yint);
            }
            System.out.println(result);
            System.out.print(prompt);
        }
    }
}
Calc.java