functional – Page 3

Property-based testing of higher-order functions

February 5, 2014 by jessitron

Property-based testing and functional programming are friends, because they’re both motivated by Reasoning About Code. Functional programming is about keeping your functions data-in, data-out so that you can reason about them. Property-based testing is about expressing the conclusions of that reasoning as properties, then showing that they’re (probably) true by testing them with hundreds of … Read moreProperty-based testing of higher-order functions

Fun with Pool-Induced Deadlock

January 29, 2014 by jessitron

Did you know that a thread can achieve deadlock with itself? It can happen in any thread pool of constrained size. Watch out for… Pool-Induced Deadlock! [1] This is easiest in a pool of size 1. Run a task in the pool, and from there, run a task in the same pool. While the outer … Read moreFun with Pool-Induced Deadlock

JVM Threads, ???, and Open Source

May 26, 2019December 16, 2013 by jessitron

Lately, open source is important to me. Today, for instance: it starts with a useful library, complicated by Java threading, confused by a Scala language feature, and ends with happiness and joy because Open Source. I’m using scalaz.concurrent.Task, a monad (LINK) with at least three special powers. First, it use a Future internally, which perform … Read moreJVM Threads, ???, and Open Source

Talk: Functional Principles for OO Developers (Ruby edition)

November 27, 2020November 27, 2013 by jessitron

Back in my early conference days, I found that I liked all the Ruby developers. So I learned Ruby in order to translate this talk into one I could give at a Ruby conference. It turned out well.

Talk: When code reacts to data

November 27, 2020November 27, 2013 by jessitron

This talk from CodeMesh 2013 talks about iteratees in Scala, among other things. Watch it on InfoQ: When Code Reacts to Data (infoq.com)

Trains within trains

May 26, 2019November 23, 2013 by jessitron

In Java, there are primitive types and there are objects. Often we want to work with everything as an object, so those primitives get boxed up into object wrappers.Ruby and Scala say, “That’s silly. Let everything be an object to begin with.” That keeps parameter-passing semantics and comparison and printing operations consistent. Yesterday while writing … Read moreTrains within trains

From lists to trains to functors

May 26, 2019November 17, 2013 by jessitron

The first useful bit of functional programming is the map method on List. It gives us a new List, which contains the results of the mapped function applied to each item in the list. We might think of it like this, mapping f over a List of a single item of type A: That’s the … Read moreFrom lists to trains to functors

Data Exposure and Encapsulation

May 26, 2019September 28, 2013 by jessitron

TL;DR – Scala lets you expose internal data, then later change underpinnings while maintaining the same interface. The functional Way is an open Way. Internal data is available to anyone who wishes to extract it. “But what about encapsulation??” – horrified OO programmer“We do not fear your code, for you cannot screw up our immutable … Read moreData Exposure and Encapsulation

A realistic use case for applicative functors

September 13, 2013 by jessitron

Applicative functor: you wrap some food in a tortilla, you wrap the microwave in a tortilla, and you get hot food in a tortilla!— Jessica Kerr (@jessitron) September 10, 2013 But why would you do that?? Say you have a collection of document IDs and you are going to retrievethe documents from the database. Not … Read moreA realistic use case for applicative functors

Idempotence in math and computing

May 26, 2019August 31, 2013 by jessitron

“Idempotent” is a big word. It’s one of the four-dollar words thrown around by functional programmers, and it confuses people — including functional programmers. This is because we don’t use it consistently. In math, idempotence describes only unary functions that you can call on their own output. Math-idempotence is, “If you take the absolute value … Read moreIdempotence in math and computing