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immutable [nfc]: Move some helpers to a general location
We'll reuse some of these in other models as we use Immutable more.
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+105
-100
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3 files changed

+105
-100
lines changed

‎src/immutableUtils.js

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/** General helpers to augment Immutable.js. */
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// @flow strict-local
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import Immutable from 'immutable';
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// Like `Immutable.Map#update`, but prune returned values equal to `zero`.
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export function updateAndPrune<K, V>(
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map: Immutable.Map<K, V>,
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zero: V,
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key: K,
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updater: (V | void) => V,
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): Immutable.Map<K, V> {
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const value = map.get(key);
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const newValue = updater(value);
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if (newValue === zero) {
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return map.delete(key);
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}
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if (newValue === value) {
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return map;
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}
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return map.set(key, newValue);
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}
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// Like `Immutable.Map#map`, but with the update-only-if-different semantics
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// of `Immutable.Map#update`. Kept for comparison to `updateAllAndPrune`.
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export function updateAll<K, V>(map: Immutable.Map<K, V>, updater: V => V): Immutable.Map<K, V> {
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return map.withMutations(mapMut => {
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map.forEach((value, key) => {
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const newValue = updater(value);
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if (newValue !== value) {
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mapMut.set(key, newValue);
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}
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});
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});
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}
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// Like `updateAll`, but prune values equal to `zero` given by `updater`.
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export function updateAllAndPrune<K, V>(
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map: Immutable.Map<K, V>,
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zero: V,
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updater: V => V,
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): Immutable.Map<K, V> {
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return map.withMutations(mapMut => {
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map.forEach((value, key) => {
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const newValue = updater(value);
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if (newValue === zero) {
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mapMut.delete(key);
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return;
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}
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if (newValue === value) {
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return; // i.e., continue
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}
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mapMut.set(key, newValue);
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});
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});
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}
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/**
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* The union of sets, represented as sorted lists.
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*
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* The inputs must be sorted (by `<`) and without duplicates (by `===`).
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*
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* The output will contain all the elements found in either input, again
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* sorted and without duplicates.
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*/
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// TODO: This implementation is Θ(n log n), because it repeatedly looks up
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// elements by numerical index. It would be nice to instead use cursors
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// within the tree to get an O(n) implementation.
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export function setUnion<T: number>(
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xs: Immutable.List<T>,
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ys: Immutable.List<T>,
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): Immutable.List<T> {
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// TODO: Perhaps build a List directly, with setSize up front.
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const result = [];
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let i = 0;
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let x = xs.get(i++);
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let j = 0;
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let y = ys.get(j++);
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while (x !== undefined && y !== undefined) {
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if (x < y) {
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result.push(x);
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x = xs.get(i++);
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} else if (x !== y) {
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result.push(y);
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y = ys.get(j++);
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} else {
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// x === y
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result.push(x);
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x = xs.get(i++);
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y = ys.get(j++);
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}
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}
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while (x !== undefined) {
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result.push(x);
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x = xs.get(i++);
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}
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while (y !== undefined) {
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result.push(y);
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y = ys.get(j++);
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}
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return Immutable.List(result);
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}

‎src/unread/__tests__/unreadModel-test.js

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@@ -2,7 +2,8 @@
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import Immutable from 'immutable';
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import { EVENT_UPDATE_MESSAGE_FLAGS } from '../../actionConstants';
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import { reducer, setUnion } from '../unreadModel';
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import { reducer } from '../unreadModel';
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import { setUnion } from '../../immutableUtils';
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import { type UnreadState } from '../unreadModelTypes';
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import * as eg from '../../__tests__/lib/exampleData';
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import { initialState, makeUnreadState } from './unread-testlib';

‎src/unread/unreadModel.js

Lines changed: 1 addition & 99 deletions
Original file line numberDiff line numberDiff line change
@@ -28,6 +28,7 @@ import {
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} from '../actionConstants';
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import DefaultMap from '../utils/DefaultMap';
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import * as logging from '../utils/logging';
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import { updateAllAndPrune, updateAndPrune, setUnion } from '../immutableUtils';
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//
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//
@@ -91,105 +92,6 @@ export const getUnreadIdsForPmNarrow = (
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const initialStreamsState: UnreadStreamsState = Immutable.Map();
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// Like `Immutable.Map#update`, but prune returned values equal to `zero`.
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function updateAndPrune<K, V>(
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map: Immutable.Map<K, V>,
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zero: V,
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key: K,
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updater: (V | void) => V,
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): Immutable.Map<K, V> {
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const value = map.get(key);
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const newValue = updater(value);
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if (newValue === zero) {
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return map.delete(key);
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}
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if (newValue === value) {
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return map;
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}
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return map.set(key, newValue);
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}
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// Like `Immutable.Map#map`, but with the update-only-if-different semantics
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// of `Immutable.Map#update`. Kept for comparison to `updateAllAndPrune`.
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/* eslint-disable-next-line no-unused-vars */
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function updateAll<K, V>(map: Immutable.Map<K, V>, updater: V => V): Immutable.Map<K, V> {
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return map.withMutations(mapMut => {
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map.forEach((value, key) => {
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const newValue = updater(value);
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if (newValue !== value) {
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mapMut.set(key, newValue);
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}
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});
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});
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}
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// Like `updateAll`, but prune values equal to `zero` given by `updater`.
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function updateAllAndPrune<K, V>(
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map: Immutable.Map<K, V>,
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zero: V,
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updater: V => V,
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): Immutable.Map<K, V> {
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return map.withMutations(mapMut => {
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map.forEach((value, key) => {
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const newValue = updater(value);
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if (newValue === zero) {
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mapMut.delete(key);
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return;
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}
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if (newValue === value) {
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return; // i.e., continue
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}
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mapMut.set(key, newValue);
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});
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});
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}
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/**
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* The union of sets, represented as sorted lists.
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*
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* The inputs must be sorted (by `<`) and without duplicates (by `===`).
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*
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* The output will contain all the elements found in either input, again
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* sorted and without duplicates.
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*/
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// TODO: This implementation is Θ(n log n), because it repeatedly looks up
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// elements by numerical index. It would be nice to instead use cursors
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// within the tree to get an O(n) implementation.
158-
export function setUnion<T: number>(
159-
xs: Immutable.List<T>,
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ys: Immutable.List<T>,
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): Immutable.List<T> {
162-
// TODO: Perhaps build a List directly, with setSize up front.
163-
const result = [];
164-
let i = 0;
165-
let x = xs.get(i++);
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let j = 0;
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let y = ys.get(j++);
168-
while (x !== undefined && y !== undefined) {
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if (x < y) {
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result.push(x);
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x = xs.get(i++);
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} else if (x !== y) {
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result.push(y);
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y = ys.get(j++);
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} else {
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// x === y
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result.push(x);
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x = xs.get(i++);
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y = ys.get(j++);
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}
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}
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while (x !== undefined) {
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result.push(x);
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x = xs.get(i++);
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}
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while (y !== undefined) {
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result.push(y);
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y = ys.get(j++);
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}
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return Immutable.List(result);
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}
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function deleteMessagesIn(
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state: UnreadStreamsState,
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streamId: number,

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