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node_modules/rxjs/src/internal/observable/partition.ts

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+import { not } from '../util/not';
+import { subscribeTo } from '../util/subscribeTo';
+import { filter } from '../operators/filter';
+import { ObservableInput } from '../types';
+import { Observable } from '../Observable';
+
+/**
+ * Splits the source Observable into two, one with values that satisfy a
+ * predicate, and another with values that don't satisfy the predicate.
+ *
+ * <span class="informal">It's like {@link filter}, but returns two Observables:
+ * one like the output of {@link filter}, and the other with values that did not
+ * pass the condition.</span>
+ *
+ * ![](partition.png)
+ *
+ * `partition` outputs an array with two Observables that partition the values
+ * from the source Observable through the given `predicate` function. The first
+ * Observable in that array emits source values for which the predicate argument
+ * returns true. The second Observable emits source values for which the
+ * predicate returns false. The first behaves like {@link filter} and the second
+ * behaves like {@link filter} with the predicate negated.
+ *
+ * ## Example
+ * Partition a set of numbers into odds and evens observables
+ * ```ts
+ * import { of, partition } from 'rxjs';
+ *
+ * const observableValues = of(1, 2, 3, 4, 5, 6);
+ * const [evens$, odds$] = partition(observableValues, (value, index) => value % 2 === 0);
+ *
+ * odds$.subscribe(x => console.log('odds', x));
+ * evens$.subscribe(x => console.log('evens', x));
+ *
+ * // Logs:
+ * // odds 1
+ * // odds 3
+ * // odds 5
+ * // evens 2
+ * // evens 4
+ * // evens 6
+ * ```
+ *
+ * @see {@link filter}
+ *
+ * @param {function(value: T, index: number): boolean} predicate A function that
+ * evaluates each value emitted by the source Observable. If it returns `true`,
+ * the value is emitted on the first Observable in the returned array, if
+ * `false` the value is emitted on the second Observable in the array. The
+ * `index` parameter is the number `i` for the i-th source emission that has
+ * happened since the subscription, starting from the number `0`.
+ * @param {any} [thisArg] An optional argument to determine the value of `this`
+ * in the `predicate` function.
+ * @return {[Observable<T>, Observable<T>]} An array with two Observables: one
+ * with values that passed the predicate, and another with values that did not
+ * pass the predicate.
+ */
+export function partition<T>(
+  source: ObservableInput<T>,
+  predicate: (value: T, index: number) => boolean,
+  thisArg?: any
+): [Observable<T>, Observable<T>] {
+  return [
+    filter(predicate, thisArg)(new Observable<T>(subscribeTo(source))),
+    filter(not(predicate, thisArg) as any)(new Observable<T>(subscribeTo(source)))
+  ] as [Observable<T>, Observable<T>];
+}