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- import { Observable } from '../Observable';
- /**
- * Groups pairs of consecutive emissions together and emits them as an array of
- * two values.
- *
- * <span class="informal">Puts the current value and previous value together as
- * an array, and emits that.</span>
- *
- * <img src="./img/pairwise.png" width="100%">
- *
- * The Nth emission from the source Observable will cause the output Observable
- * to emit an array [(N-1)th, Nth] of the previous and the current value, as a
- * pair. For this reason, `pairwise` emits on the second and subsequent
- * emissions from the source Observable, but not on the first emission, because
- * there is no previous value in that case.
- *
- * @example <caption>On every click (starting from the second), emit the relative distance to the previous click</caption>
- * var clicks = Rx.Observable.fromEvent(document, 'click');
- * var pairs = clicks.pairwise();
- * var distance = pairs.map(pair => {
- * var x0 = pair[0].clientX;
- * var y0 = pair[0].clientY;
- * var x1 = pair[1].clientX;
- * var y1 = pair[1].clientY;
- * return Math.sqrt(Math.pow(x0 - x1, 2) + Math.pow(y0 - y1, 2));
- * });
- * distance.subscribe(x => console.log(x));
- *
- * @see {@link buffer}
- * @see {@link bufferCount}
- *
- * @return {Observable<Array<T>>} An Observable of pairs (as arrays) of
- * consecutive values from the source Observable.
- * @method pairwise
- * @owner Observable
- */
- export declare function pairwise<T>(this: Observable<T>): Observable<[T, T]>;
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