add bool factory

src/lib/utils/operators.ts

@@ -27,3 +27,12 @@ export function shareDistinctLast<T>(values = 1): UnaryFunction<Observable<T>, O
 
 export const toLengthValue = (entities: unknown[]): number => entities?.length ?? 0;
 export const getLength = pipe(map(toLengthValue), distinctUntilChanged());
+
+export function boolFactory<T>(obs: Observable<T>, project: (value: T) => boolean): Observable<boolean>[] {
+    const result = obs.pipe(map(project), shareDistinctLast());
+    const inverse = result.pipe(
+        map(value => !value),
+        shareDistinctLast(),
+    );
+    return [result, inverse];
+}