functions.py

import arith

'''
Contains the implemented functions and their names. This dictionary
is referenced when checking whether or not a command entered is a valid
function. The dictionary contains of key: value pairs, where key is a string
containing the function name and value is a reference to the function that
was implemented.
In case a new function is added to the calculator, make sure to update this
dictionary.
'''
function_table = {
    'sub': arith.sub,
    'sum': arith.sum,
    'divide': arith.divide,
    'multiply': arith.multiply,
    'power': arith.power,
    'sqrt': arith.sqrt,
    'mod': arith.mod,
    'gcd': arith.gcd,
    'lcm': arith.lcm,
    'bin': arith.bin
}

arity_table = {
    'sub': 2,
    'sum': 2,
    'divide': 2,
    'multiply': 2,
    'power': 2,
    'sqrt': 1,
    'mod': 2,
    'gcd': 2,
    'lcm': 2,
    'bin': 1
}

types_table = {
    'sub': int,
    'sum': int,
    'divide': int,
    'multiply': int,
    'power': int,
    'sqrt': int,
    'mod': int,
    'gcd': int,
    'lcm': int,
    'bin': str
}

'''
Returns True if function_name provided is a valid function, else False.
'''
def is_function(function_name):
    return function_name in function_table

'''
Returns the function according to function_name.
'''
def get_function(function_name):
    return function_table[function_name]

'''
Returns the arity of the function according to function_name.
'''
def get_arity(function_name):
    return arity_table[function_name]

'''
Returns the type of _all_ parameters of the function according to function_name.
'''
def get_type(function_name):
    return types_table[function_name]

'''
Prints the available functions and their arity.
'''
def print_functions():
    print('supported functions:')
    for function_name in function_table.keys():
        print('"%s" arity: %i' % (function_name, arity_table[function_name]))

'''
Processes the given input
'''
def process_line(expression):
    # Tokenize string
    expression = expression.split()
    operands = []

    for x in expression:    
        # Is the token a function name?
        if is_function(x):    
            # Retrieve function
            function_name = x
        # Is the token an operand?
        elif x.isnumeric():
            # Correct type
            try:
                # Store operand
                operands.append(get_type(function_name)(x))
            # Wrong type
            except:
                # Output: 'invalid operand type'
                print('invalid operand type')
        # Otherwise
        else:
            # Output: unknown token'
            print('unknown token')
            return
    
    # Correct arity?
    if get_arity(function_name) == len(operands):
        # Call function and output result
        print(get_function(function_name)(*operands))
    # Otherwise
    else:
        # Output: 'Invalid number of operands'
        print('invalid number of operands')