future

A look at how exceptions work with Scala Futures and the onComplete ‘Failure’ case alvin September 18, 2017 - 12:53pm

Here’s a little example of how exceptions work with Scala Futures, specifically looking at the onComplete ‘Failure’ case.

In this example I start three Futures that run for different lengths of time, and the shortest-running Future throws an exception:

How to use multiple Futures in a Scala for-comprehension

If you want to create multiple Scala Futures and merge their results together to get a result in a for comprehension, the correct approach is to (a) first create the futures, (b) merge their results in a for comprehension, then (c) extract the result using onComplete or a similar technique.

8 ways to do asynchronous processing in Android and counting alvin August 3, 2017 - 5:27pm

This is a good article that shows several different ways to handle background tasks in Android, including

  • AsyncTask
  • IntentService
  • Loader
  • JobScheduler
  • CountdownTimer
  • Java threads
  • Android HandlerThread
  • FutureTask
  • Java Timer

The karma of writing a book

As I’m writing my new book on functional programming in Scala I started thinking, “What if the person who creates Skynet or the Matrix reads this book and suddenly understands how to create their evil invention? But ... if I don’t create this book, they’ll stay on their previous course in life to be a world-famous cookie baker.”

It’s quite a responsibility, knowing that you could be responsible for a future without great cookies.

Don’t let yesterday contain the greatest things you’ve ever done

Via a friend on Facebook:

“My advice: Don’t let yesterday contain the greatest things you’ve ever done. Make tomorrow contain your next great goal. Because once you feel your greatest days are behind you, you begin to die.”

At the very least that quote is about the importance of having goals.

The state of payments systems in ten years

“If you think you know what the state of the payments system 10 years out you're in a state of delusion.”

~ Charlie Munger talking about AMEX

Scala ‘for loop’ examples and syntax

Table of Contents1 - Example data structures2 - Basic for-loop examples3 - Generators in for-loops4 - for-loop generators with guards5 - Scala for/yield examples (for-expressions)6 - Scala for loop counters (and zip, zipWithIndex)7 - Using a for loop with a Map8 - Multiple futures in a for loop9 - foreach examples10 - Summary

Besides having a bad memory, I haven’t been able to work with Scala much recently, so I’ve been putting together this list of for loop examples.

This page is currently a work in progress, and as of tonight I haven’t tested some of the examples, but ... if you’re looking for some Scala for loop examples — technically called a for comprehension or for expression — I hope these examples are helpful.