import { AlphaCtx } from "../../core";
import { Env } from "../../env";
import * as Exps from "../../exps";
export declare class NilClsCore extends Exps.ClsCore {
    append(cls: Exps.ClsCore): Exps.ClsCore;
    get field_names(): Array<string>;
    evaluate(env: Env): Exps.ClsValue;
    fields_repr(): Array<string>;
    repr(): string;
    fields_alpha_repr(ctx: AlphaCtx): Array<string>;
    alpha_repr(ctx: AlphaCtx): string;
}