homework_04.js

    function Stack() {
        this.array = [];
    }

    Stack.prototype.push = function (insert) {
        this.array.push(insert);
    }
    Stack.prototype.pop = function () {
        return this.array.pop();
    }
    Stack.prototype.peek = function () {
        return this.array[this.array.length - 1];
    }
    Stack.prototype.isEmpty = function () {
        return this.array.length == 0;
    }



    function rpn(stringa) {
        var stack = new Stack();
        var z = stringa.split(" ");
        for (var i = 0; i < z.length; i++) {
            var ris = 0;
            switch (z[i]) {
                case "+":
                    ris = stack.pop();
                    ris += stack.pop();
                    stack.push(ris);
                    break;
                case "-":
                    ris = stack.pop();
                    ris = stack.pop() - ris;
                    stack.push(ris);
                    break;
                case "*":
                    ris = stack.pop();
                    ris *= stack.pop();
                    stack.push(ris);
                    break;
                case "/":
                    ris = stack.pop();
                    ris = stack.pop() / ris;
                    stack.push(ris);
                    break;
                case "^":
                    ris = stack.pop();
                    ris = Math.pow(ris, stack.pop());
                    stack.push(ris);
                    break;

                default:
                    stack.push(parseInt(z[i]));
            }
        }
        return stack.pop();
    }