Interpreter 1: No Scope (excerpt)

scheme.py

class Procedure:
    def __init__(self, parameters, expressions, env):
        self.parameters = parameters
        self.expressions = expressions
        self.env = env

    def __call__(self, *args):
        for expression in self.expressions:        # Substitute the arguments for parameter names
            for names, values in zip(self.parameters, args):
                expression = substitute(expression, names, values)

            result = seval(expression,             # Evaluate the resulting expression
                           dict(self.env))         # makes a copy of env
        return result