import { type DropInitialValueOperator, type Observable } from '../types/index.mjs';
/**
 * Samples the current value from another observable each time the source emits.
 * Emits a tuple of [sourceValue, sampledValue].
 *
 * @template A - The type of values from the source observable
 * @template B - The type of values from the sampled observable
 * @param observable - The observable to sample from
 * @returns An operator that emits tuples of source and sampled values
 *
 * @example
 * ```ts
 * //  Timeline:
 * //
 * //  name$     "Alice"           "Bob"               "Charlie"
 * //  age$                25              30
 * //  result$   (skip)          ["Bob",25]           ["Charlie",30]
 * //
 * //  Explanation:
 * //  - withCurrentValueFrom samples the current value from another observable
 * //  - Emits a tuple [sourceValue, sampledValue] each time the SOURCE emits
 * //  - Does NOT emit when the sampled observable (age$) emits
 * //  - Does not emit until both observables have emitted at least once
 * //  - "Alice" is skipped because age$ hasn't emitted yet
 *
 * const name$ = source<string>();
 *
 * const age$ = source<number>();
 *
 * const result$ = name$.pipe(withCurrentValueFrom(age$));
 *
 * const valueHistory: (readonly [string, number])[] = [];
 *
 * result$.subscribe(([name_, currentAge]) => {
 *   valueHistory.push([name_, currentAge]);
 * });
 *
 * name$.next('Alice'); // nothing logged (age$ hasn't emitted)
 *
 * assert.deepStrictEqual(valueHistory, []);
 *
 * age$.next(25);
 *
 * name$.next('Bob'); // logs: Bob is 25 years old
 *
 * assert.deepStrictEqual(valueHistory, [['Bob', 25]]);
 *
 * age$.next(30);
 *
 * name$.next('Charlie'); // logs: Charlie is 30 years old
 *
 * assert.deepStrictEqual(valueHistory, [
 *   ['Bob', 25],
 *   ['Charlie', 30],
 * ]);
 * ```
 */
export declare const withCurrentValueFrom: <A, B>(observable: Observable<B>) => DropInitialValueOperator<A, readonly [A, B]>;
/**
 * Alias for `withCurrentValueFrom`.
 * @see withCurrentValueFrom
 */
export declare const withLatestFrom: <A, B>(observable: Observable<B>) => DropInitialValueOperator<A, readonly [A, B]>;
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