import type { Option } from "../Option";
/**
 * Atomically modifies the `FiberRef` with the specified partial function, which computes
 * a return value for the modification if the function is defined in the current value
 * otherwise it returns a default value.
 * This is a more powerful version of `updateSome`.
 */
export declare function modifySome<B>(defaultValue: () => B): <A>(f: (a: A) => Option<[B, A]>) => (fiberRef: import("./fiberRef").FiberRef<A>) => import("../Effect").UIO<B>;
//# sourceMappingURL=modifySome.d.ts.map