engine_peter.py

"""
Engine class of the RPN Calculator
"""

import math

class rpn_engine:
    def __init__(self):
        """ Constructor """
        self.stack = []

    def push(self, number):
        """ push a value to the internal stack """
        self.stack.append(number)

    def pop(self):
        """ pop a value from the stack """
        try:
            return self.stack.pop()
        except IndexError:
            pass # do not notify any error if the stack is empty...

    def sum_two_numbers(self):
        op2 = self.stack.pop()
        op1 = self.stack.pop()
        self.push(op1 + op2)

    def subtract_two_numbers(self):
        op2 = self.stack.pop()
        op1 = self.stack.pop()
        self.push(op1 - op2)

    def multiply_two_numbers(self):
        op2 = self.stack.pop()
        op1 = self.stack.pop()
        self.push(op1 * op2)

    def divide_two_numbers(self):
        op2 = self.stack.pop()
        op1 = self.stack.pop()
        self.push(op1 / op2)

    def pow2_a_number(self):
        op1 = self.stack.pop()
        self.push(op1 * op1)

    def sqrt_a_number(self):
        op1 = self.stack.pop()
        self.push(math.sqrt(op1))


    def compute(self, operation):
        """ compute an operation """

        if operation == '+':
            self.sum_two_numbers()

        if operation == '-':
            self.subtract_two_numbers()

        if operation == '*':
            self.multiply_two_numbers()

        if operation == '/':
            self.divide_two_numbers()

        if operation == '^2':
            self.pow2_a_number()

        if operation == 'SQRT':
            self.sqrt_a_number()

        if operation == 'C':
            self.stack.pop()

        if operation == 'AC':
            self.stack.clear()