import type { PropFormula } from "../../../models";
/**
 * Applies negation introduction rule:
 * If (A => B) and (A => ~B), then we can infer ~A.
 *
 * @param formulas - An array of propositional formulas.
 * @returns {[PropFormula]} A tuple containing the inferred formula.
 * @throws {Error} if negation introduction rule is not applicable.
 */
export declare function negationIntroduction(formulas: PropFormula[]): [PropFormula];