import { GrammarTreeVisitor } from "../../tree/walkers/GrammarTreeVisitor.js";
import { FrequencySet } from "../../misc/FrequencySet.js";
import { ActionAST } from "../../tool/ast/ActionAST.js";
import { GrammarAST } from "../../tool/ast/GrammarAST.js";
import { TerminalAST } from "../../tool/ast/TerminalAST.js";
export declare class ElementFrequenciesVisitor extends GrammarTreeVisitor {
    /**
     * This special value means "no set", and is used by {@link minFrequencies} to ensure that {@link combineMin}
     * doesn't merge an empty set (all zeros) with the results of the first alternative.
     */
    private static readonly sentinel;
    readonly frequencies: Array<FrequencySet<string>>;
    readonly minFrequencies: Array<FrequencySet<string>>;
    /**
     * Generate a frequency set as the union of two input sets. If an element is contained in both sets, the value
     * for the output will be the maximum of the two input values.
     *
     * @param a The first set.
     * @param b The second set.
     *
     * @returns The union of the two sets, with the maximum value chosen whenever both sets contain the same key.
     */
    protected static combineMax(a: FrequencySet<string>, b: FrequencySet<string>): FrequencySet<string>;
    /**
     * Generate a frequency set as the union of two input sets. If an element is contained in both sets, the value
     * for the output will be the minimum of the two input values.
     *
     * @param a The first set.
     * @param b The second set. If this set is {@link sentinel}, it is treated as though no second set were provided.
     *
     * @returns The union of the two sets, with the minimum value chosen whenever both sets contain the same key.
     */
    protected static combineMin(a: FrequencySet<string>, b: FrequencySet<string>): FrequencySet<string>;
    /**
     * Generate a frequency set as the union of two input sets, with the values clipped to a specified maximum value.
     * If an element is contained in both sets, the value for the output, prior to clipping, will be the sum of the
     * two input values.
     *
     * @param a The first set.
     * @param b The second set.
     * @param clip The maximum value to allow for any output.
     *
     * @returns The sum of the two sets, with the individual elements clipped to the maximum value given by `clip`.
     */
    protected static combineAndClip(a: FrequencySet<string>, b: FrequencySet<string>, clip: number): FrequencySet<string>;
    protected tokenRef(ref: TerminalAST): void;
    protected ruleRef(ref: GrammarAST, arg: ActionAST): void;
    protected stringRef(ref: TerminalAST): void;
    protected enterAlternative(): void;
    protected exitAlternative(): void;
    protected enterElement(): void;
    protected exitElement(): void;
    protected enterBlockSet(): void;
    protected exitBlockSet(): void;
    protected exitSubrule(tree: GrammarAST): void;
    protected enterLexerAlternative(): void;
    protected exitLexerAlternative(): void;
    protected enterLexerElement(): void;
    protected exitLexerElement(): void;
    protected exitLexerSubrule(tree: GrammarAST): void;
}