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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>];
}
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