Created
December 13, 2017 12:25
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""" | |
Engine class of the RPN Calculator | |
""" | |
import math | |
class rpn_engine: | |
def __init__(self): | |
""" Constructor """ | |
self.stack = [] | |
self.catalog = self.get_functions_catalog() | |
def get_functions_catalog(self): | |
return {"+": self.sum_two_numbers, | |
"-": self.subtract_two_numbers, | |
"*": self.multiply_two_numbers, | |
"/": self.divide_two_numbers, | |
"^2": self.pow2_a_number, | |
"SQRT": self.sqrt_a_number, | |
"C": self.stack.pop, | |
"AC": self.stack.clear} | |
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, op1, op2): | |
return op1 + op2 | |
def subtract_two_numbers(self, op1, op2): | |
return op1 - op2 | |
def multiply_two_numbers(self, op1, op2): | |
return op1 * op2 | |
def divide_two_numbers(self, op1, op2): | |
return op1 / op2 | |
def pow2_a_number(self, op1): | |
return op1 * op1 | |
def sqrt_a_number(self, op1): | |
return math.sqrt(op1) | |
def compute(self, operation): | |
""" compute an operation """ | |
if operation in ['+', '-', '*', '/']: | |
self.compute_operation_with_two_operands(self.catalog[operation]) | |
if operation in ['^2', 'SQRT']: | |
self.compute_operation_with_one_operand(self.catalog[operation]) | |
if operation in ['C', 'AC']: | |
self.compute_operation_with_no_operands(self.catalog[operation]) | |
def compute_operation_with_two_operands(self, operation): | |
""" exec operations with two operands """ | |
try: | |
if len(self.stack) < 2: | |
raise BaseException("Not enough operands on the stack") | |
op2 = self.stack.pop() | |
op1 = self.stack.pop() | |
result = operation(op1, op2) | |
self.push(result) | |
except BaseException as error: | |
print(error) | |
def compute_operation_with_one_operand(self, operation): | |
""" exec operations with one operand """ | |
try: | |
op1 = self.stack.pop() | |
result = operation(op1) | |
self.push(result) | |
except BaseException as error: | |
print(error) | |
def compute_operation_with_no_operands(self, operation): | |
""" exec operations with no operands """ | |
try: | |
operation() | |
except BaseException as error: | |
print(error) |
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