A Boolean valuation assigns each primitive proposition a value in , equivalently , and extends recursively to every propositional formula using the classical logical connectives. The same primitive proposition always receives the same value within one Boolean valuation. For compound propositional formulas and ,Every other case receives the opposite value. Thus gives . A truth table varies the assignment; recursive evaluation computes one row. The truth-functional restriction means that changing what the primitive propositions describe, while retaining their values, cannot change the value of the compound propositional formula. See forall x: Calgary, chapter 9 and section 10.1.
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