More On Types

Recently I wrote a cute little program for doing Turtle Graphics. For those of you who don't know, turtle graphics were originally added to the LOGO language by Seymour Papert in the late 1960s. He built a robot that he called a "turtle" that could hold a pen. The robot had wheels and could move forwards and backwards, and could rotate left and right....

Jun 2021

On Types

I wrote my first program in 1964. The name of the program was: Mr Patternson's Computerized Gate, and it was implemented on a little plastic computer named DIGICOMP-I, which was a cute little three bit finite state machine with 6 AND gates. The first electronic computer I ever wrote a program for was an ECP-18 in 1966. This was a 15 bit wide machine...

Jun 2021

if-else-switch

A few days ago someone tweeted a question asking which of the following PHP snippets was better than the others, or whether there might be an even better approach. I tweeted my answer in the following cryptic paragraph. Place the if/else cases in a factory object that creates a polymorphic object for each variant. Create the factory...

Mar 2021

Pairing Guidelines

Everybody pairs from time to time. It is a rare programmer who has not sat down with another programmer to look something over or help find a bug. Deep problems, that require much heavy thinking, do not often lend themselves to pairing. The interaction between the programmers tends to disrupt the necessary concentration. On the other hand, it...

Jan 2021

Solid Relevance

Recently I received a letter from someone with a concern. It went like this: For years the knowledge of the SOLID principle has been a standard part of our recruiting procedure. Candidates were expected to have a good working knowledge of these principles. Lately, however, one of our managers, who doesn’t code much anymore, has questioned...

Oct 2020

Loopy

The following is a segment of a journey. It has no obvious beginning point, nor does it actually end up anywhere. The value, if any, is in the journey itself. The code below is the standard solution to the Prime Factors Kata. public List<Integer> factorsOf(int n) { ArrayList<Integer> factors = new ArrayList<>(); ...

Oct 2020

Conference Conduct

It was just a few years ago, at the height of the Me Too revelations, that codes of conduct began to prominently appear in Software Conferences. At the time I felt this was appropriate given the horror stories that had been circulating about sexual harassment and misbehavior at some of those conferences. I wrote a blog about it at the time. Since...

Sep 2020

The Disinvitation

I have a friend, in the Chicago area, who calls me up two or three times a year to ask me to give a talk at a User Group, or a conference he’s involved with, or something like that. If my schedule is free I always say yes. I don’t charge anything because I enjoy supporting the Chicago software community, and it’s never a bad thing to get my face out...

Sep 2020

REPL Driven Design

If you follow me on facebook you know that I’ve been publishing daily CoronaVirus statistics. I generate these statistics using the daily updates in the Johns Hopkins github repository. At first I just hand copied the data into a spreadsheet. But that became tedious quite rapidly. Then, in late March, I wrote a little Clojure program to extract...

May 2020

A Little More Clojure

So let’s learn just a little bit more of Clojure. Here are a few common utility functions: user=> (inc 1) ; increments argument 2 user=> (dec 3) ; decrements argument 2 user=> (empty? []) ; tests for empty true user=> (empty? [1 2]) false If you know Java or C# you probably know what the map function does. Here’s an example:...

Apr 2020