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/** https://docs.evt.land/api/operator */export type Operator<T, U> =    Operator.fλ<T, U> |    ((data: U) => boolean) | //Filter    (U extends T ? (data: T) => data is U : never) //Type guard    ;
export namespace Operator {
    export type fλ<T, U> =        fλ.Stateless<T, U> |        fλ.Stateful<T, U>        ;
    export namespace fλ {
        export type Stateless<T, U> = (data: T, registerSideEffect: (sideEffect: () => void) => void) => readonly [U] | null;
        export type Stateful<T, U> = [            (data: T, prev: U, registerSideEffect: (sideEffect: () => void)=> void) => readonly [U] | null,            U //Seed        ];
    }
    export type Stateless<T, U> =        fλ.Stateless<T, U> |        ((data: U) => boolean) |        (U extends T ? (data: T) => data is U : never)        ;
}