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outer
  .pipe(concatMap(createInner))
  .subscribe(x => console.log("[concatMap] outer:", x), undefined, () =>
    console.log("[concatMap] done!")
  );

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function sleep(ms: number) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

function createInner(x: number) {
  return new Observable(obs => {
    (async () => {
      for (let i = 0; i < 3; i++) {
        if (i > 0) await sleep(500);
        obs.next(10 * x);

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function computeSquaredSum(): OperatorFunction<number, number> {
  return source =>
    source.pipe(
      map(n => n * n),
      reduce((s, n) => s + n, 0),
    );
}
oneThroughTen
  .pipe(computeSquaredSum())
  .subscribe(x => console.log("Squared sum w/ custom op =", x));

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const oneThroughTen = of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

oneThroughTen
  .pipe(
    map(n => n * n),
    reduce((s, n) => s + n, 0)
  )
  .subscribe(sqSum => console.log("Squared sum =", sqSum));

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function fromEvent<T extends Event = Event>(
  target: EventTarget,
  eventName: string
): Observable<T> {
  return new Observable(obs => {
    const listener: EventListener = (evt: T) => {
      obs.next(evt);
    };
    target.addEventListener(eventName, listener);
    return () => target.removeEventListener(eventName, listener);

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function of<T>(...values: T[]): Observable<T> {
  return new Observable(obs => {
    for (const value of values) {
      obs.next(value);
    }
    obs.complete();
  });
}

// Logs:

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const observable = new Observable(subscriber => {
  subscriber.next(1);
  subscriber.next(2);
  subscriber.next(3);
  setTimeout(() => {
    subscriber.next(4);
    subscriber.complete();
  }, 1000);
});

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interface Observer<T> {
  next(value: T): void;
  error(err: any): void;
  complete(): void;
}

interface Subscription {
  unsubscribe(): void;
}
  

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# ipython-utils/researchenv/magics.py

from IPython.core.magic import Magics, magics_class, cell_magic, needs_local_scope
from IPython.core.magic_arguments import magic_arguments, argument, parse_argstring
from IPython.core.interactiveshell import InteractiveShell
from IPython.core.display import display
from google.cloud import bigquery

@magics_class
class ResearchEnvMagics(Magics):

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# ipython-utils/researchenv/__init__.py

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
from IPython.core.interactiveshell import InteractiveShell

def load_ipython_extension(ipython: InteractiveShell):
    print('%matplotlib inline')