import { UIO } from './IO/fluent';
export interface Ref<A> {
    read: UIO<A>;
    write: (a: A) => UIO<void>;
    modify: <B>(f: (a: A) => [B, A]) => UIO<B>;
    update: (f: (a: A) => A) => UIO<A>;
    update_: (f: (a: A) => A) => UIO<void>;
}
export declare class IORef<A> implements Ref<A> {
    private value;
    static make: <A_1>(a: A_1) => UIO<IORef<A_1>>;
    private constructor();
    read: UIO<A>;
    write: (a: A) => UIO<void>;
    modify: <B>(f: (a: A) => [B, A]) => UIO<B>;
    update: (f: (a: A) => A) => UIO<A>;
    update_: (f: (a: A) => A) => UIO<void>;
}