/** PURE_IMPORTS_START tslib,_Subscriber PURE_IMPORTS_END */
import * as tslib_1 from "tslib";
import { Subscriber } from '../Subscriber';
export function pairwise() {
    return function (source) { return source.lift(new PairwiseOperator()); };
}
var PairwiseOperator = /*@__PURE__*/ (function () {
    function PairwiseOperator() {
    }
    PairwiseOperator.prototype.call = function (subscriber, source) {
        return source.subscribe(new PairwiseSubscriber(subscriber));
    };
    return PairwiseOperator;
}());
var PairwiseSubscriber = /*@__PURE__*/ (function (_super) {
    tslib_1.__extends(PairwiseSubscriber, _super);
    function PairwiseSubscriber(destination) {
        var _this = _super.call(this, destination) || this;
        _this.hasPrev = false;
        return _this;
    }
    PairwiseSubscriber.prototype._next = function (value) {
        var pair;
        if (this.hasPrev) {
            pair = [this.prev, value];
        }
        else {
            this.hasPrev = true;
        }
        this.prev = value;
        if (pair) {
            this.destination.next(pair);
        }
    };
    return PairwiseSubscriber;
}(Subscriber));
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