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1import { OperatorFunction } from '../types';
2/**
3 * Groups pairs of consecutive emissions together and emits them as an array of
4 * two values.
5 *
6 * <span class="informal">Puts the current value and previous value together as
7 * an array, and emits that.</span>
8 *
9 * ![](pairwise.png)
10 *
11 * The Nth emission from the source Observable will cause the output Observable
12 * to emit an array [(N-1)th, Nth] of the previous and the current value, as a
13 * pair. For this reason, `pairwise` emits on the second and subsequent
14 * emissions from the source Observable, but not on the first emission, because
15 * there is no previous value in that case.
16 *
17 * ## Example
18 *
19 * On every click (starting from the second), emit the relative distance to the previous click
20 *
21 * ```ts
22 * import { fromEvent, pairwise, map } from 'rxjs';
23 *
24 * const clicks = fromEvent<PointerEvent>(document, 'click');
25 * const pairs = clicks.pipe(pairwise());
26 * const distance = pairs.pipe(
27 * map(([first, second]) => {
28 * const x0 = first.clientX;
29 * const y0 = first.clientY;
30 * const x1 = second.clientX;
31 * const y1 = second.clientY;
32 * return Math.sqrt(Math.pow(x0 - x1, 2) + Math.pow(y0 - y1, 2));
33 * })
34 * );
35 *
36 * distance.subscribe(x => console.log(x));
37 * ```
38 *
39 * @see {@link buffer}
40 * @see {@link bufferCount}
41 *
42 * @return A function that returns an Observable of pairs (as arrays) of
43 * consecutive values from the source Observable.
44 */
45export declare function pairwise<T>(): OperatorFunction<T, [T, T]>;
46//# sourceMappingURL=pairwise.d.ts.map
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