public static function equiv($constraintA, $constraintB) {
        return function ($features) use ($constraintA, $constraintB) {
            return $constraintA($features) === $constraintB($features);
        };
    }
public static function equiv($constraintA, $constraintB) {
        return function ($features) use ($constraintA, $constraintB) {
            return $constraintA($features) === $constraintB($features);
        };
    }
public static function equiv ( $ constraintA , $ constraintB ) { return function ( $ features ) use ( $ constraintA , $ constraintB ) { return $ constraintA ( $ features ) === $ constraintB ( $ features ) ; } ; }
Returns a formula that is the biconditional of two formulas.
@param callable $constraintA
@param callable $constraintB
@return callable
Returns a formula that is the biconditional of two formulas .