Build a Rule EngineStep 5 of 5

Compose a Real Rule

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Step 5 - Compose a Real Rule

Put it together into a feature-flag / access rule.

Implement the helper evaluate(rule, context) that simply calls rule.interpret(context). Then confirm a composed rule such as

And(Equals("country", "US"), Var("age_verified"))

evaluates correctly against different context dicts. The whole tree is driven by the single interpret contract every node shares.

Hints
Starter code
class Var:
    def __init__(self, name):
        self.name = name

    def interpret(self, context):
        return bool(context.get(self.name, False))


class Const:
    def __init__(self, value):
        self.value = value

    def interpret(self, context):
        return self.value


class And:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def interpret(self, context):
        return self.a.interpret(context) and self.b.interpret(context)


class Or:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def interpret(self, context):
        return self.a.interpret(context) or self.b.interpret(context)


class Not:
    def __init__(self, expr):
        self.expr = expr

    def interpret(self, context):
        return not self.expr.interpret(context)


class Equals:
    def __init__(self, key, value):
        self.key = key
        self.value = value

    def interpret(self, context):
        return context.get(self.key) == self.value


def evaluate(rule, context):
    """Evaluate a composed rule tree against a context dict."""
    # TODO: return rule.interpret(context)
    pass
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