compiler.py

from functools import reduce
import sys

from grammar import (
    Program,
    Statement,
    Function,
    ArgumentList,
    Argument,
    Integer,
    FunctionCall,
)


def add_func(*args):
    return reduce(lambda a, x: a + x, args)

def mul_func(*args):
    return reduce(lambda a, x: a * x, args)

def print_func(*args):
    return ' '.join([str(_) for _ in args])

functions = {
    'ADD': (float('inf'), add_func),
    'MUL': (float('inf'), mul_func),
    'PRINT': (float('inf'), print_func),
}

def resolve_function_call(node):
    name = node.find(Function).string
    nargs, func = functions[name]

    arg_nodes = node.find(ArgumentList)[0].find_all(Argument)
    resolved_args = []
    for arg in arg_nodes:
        arg = arg.elements[0]
        if isinstance(arg, Integer):
            resolved_args.append(int(arg.string))
        elif isinstance(arg, FunctionCall):
            resolved_args.append(resolve_function_call(arg))
        else:
            print('lolwtf')

    return func(*resolved_args)


if __name__ == '__main__':
    source = open(sys.argv[1]).read()
    parser = Program.parser()
    result = parser.parse_string(source)

    # Execute the program
    for statement in result.find_all(Statement):
        print('>>', statement.string)
        resolve_me = statement.find(FunctionCall)

        try:
            print('   RESULT:', resolve_function_call(resolve_me))
        except:
            print('   ERROR: statement is not valid')
            raise

grammar.py

import modgrammar as mg

mg.grammar_whitespace_mode = 'optional'


class Integer(mg.Grammar):
    grammar = mg.WORD('0-9')


class Argument(mg.Grammar):
    grammar = (Integer | mg.REF('FunctionCall'))


class ArgumentList(mg.Grammar):
    grammar = mg.OPTIONAL(mg.LIST_OF(Argument, sep=','))


class Function(mg.Grammar):
    grammar = mg.WORD('A-Za-z_')


class FunctionCall(mg.Grammar):
    grammar = (Function, '(', ArgumentList, ')')


class Statement(mg.Grammar):
    grammar = (FunctionCall, ';')


class Ignore(mg.Grammar):
    grammar = (mg.BOL, mg.EOL)


class Program(mg.Grammar):
    grammar = (mg.ZERO_OR_MORE(Statement | Ignore), mg.EOF)

test.out

>> ADD(MUL(2, 2), 3);
   RESULT: 7
>> PRINT(1, 2, 3, ADD(1, 1, 2), MUL(5, 1));
   RESULT: 1 2 3 4 5

test.prog

ADD(MUL(2, 2), 3);
PRINT(1, 2, 3, ADD(1, 1, 2), MUL(5, 1));