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The syntax of the IIf function is as follows: IIf(expr, truepart, falsepart) All three parameters are required: e expr is the expression that is to be evaluated. truepart defines what the IIf function returns if the evaluation of expr returns true. falsepart defines what the IIf function returns if the evaluation of expr returns false.
Unlike a true ternary operator however, both of the results are evaluated prior to performing the comparison. For example, if one of the results is a call to a function which inserts a row into a database table, that function will be called whether or not the condition to return that specific result is met.
In other words, it asks whether the formula's variables can be consistently replaced by the values TRUE or FALSE to make the formula evaluate to TRUE. If this is the case, the formula is called satisfiable, else unsatisfiable. For example, the formula "a AND NOT b" is satisfiable because one can find the values a = TRUE and b = FALSE, which ...
The logical NAND is an operation on two logical values, typically the values of two propositions, that produces a value of false if both of its operands are true. In other words, it produces a value of true if at least one of its operands is false. The truth table for p NAND q (also written as p ↑ q, Dpq, or p | q) is as follows:
The corresponding logical symbols are "", "", [6] and , [10] and sometimes "iff".These are usually treated as equivalent. However, some texts of mathematical logic (particularly those on first-order logic, rather than propositional logic) make a distinction between these, in which the first, ↔, is used as a symbol in logic formulas, while ⇔ is used in reasoning about those logic formulas ...
In propositional logic, a propositional formula is a type of syntactic formula which is well formed. If the values of all variables in a propositional formula are given, it determines a unique truth value. A propositional formula may also be called a propositional expression, a sentence, [1] or a sentential formula.
For instance, counterfactual conditionals would all be vacuously true on such an account, when in fact some are false. [ 8 ] In the mid-20th century, a number of researchers including H. P. Grice and Frank Jackson proposed that pragmatic principles could explain the discrepancies between natural language conditionals and the material conditional.
A formula is logically valid (or simply valid) if it is true in every interpretation. [22] These formulas play a role similar to tautologies in propositional logic. A formula φ is a logical consequence of a formula ψ if every interpretation that makes ψ true also makes φ true. In this case one says that φ is logically implied by ψ.