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Overloaded Operators

Pascal addition expression.

E[[E₁+E₂]] = lambda e.lambda s.
    cases (E[[E₁]]e s) of
        isNat(n₁) -> (cases (E[[E₂]]e s) of
            isNat(n₂) -> inNat(n₁ plus n₂)
            ...end)
        ...
        [] isRat(r₁) -> (cases (E[[E₂]]e s) of
            ...
            [] isRat(r₂) -> inRat(r₁ addrat r₂)
            ...end)
        ...
        [] isSet(t₁) -> ...inSet(t₁ union t₂) ...
        ...
    end

Pre-execution analysis -> actual operation can be determined at compile-time.