This post is about trees — the computer science kind, as illustrated in Figure 1 below. Our goal is to see how trees can be derived from text and, conversely, how trees can be turned back into text. …

The other day I needed a little server app that would receive data as an HTTP request and save it on disk in a specified directory. Each data record consisted of a file path and the the file contents in the form { fileName: String, contents: String } The request…

For a while now, I’ve been working on a variant/subset of LaTeX which I call MiniLaTeX. The idea is to be able write MiniLaTeX documents in the browser and also to have them rendered there … indeed, to have them rendered in real-time as the user types. Good for writing…

I’d like to announce the Alpha4 Release of minilatex.lamdera.app, an app for doing LaTeX in the browser—a great way to publish class notes, problem sets, etc., along with many other uses. I’ve used the app a good deal myself, but now, to make it fulfill its purpose, I need feedback…

As a fun exercise, I decided to try to make a Lisp using Elm … not the whole deal, of course, but just a little piece to see what is possible and how one would do it. The result, which I will describe here, is a skeleton of a very…

The functional programming language Elm is best known for writing web apps. You can also use Elm to write a headless “black box” app that you talk to via the terminal. Here is a sample session:

In a previous post, I discussed an Elm implementation of the mini-language Arith discussed in Benjamin Peirce’s book Types and Programming Languages (TAPL). The implementation provides a parser and an eval function, so we can do things like this: > parse "succ succ 0" Ok (Succ (Succ Zero)) > parse…

The Elm programming language is best known for building web apps. Turns out, however, that one can also build something quite different: command-line programs like the one you see on the left. It is a simple stack-based calculator. The first command computes 2 + 3 and leaves 5 on the…

Get the physics right, then the code! In this article, we will design a little light meter, making sure that we get the whole pipeline right: the physics, the math, the code, and the wiring. The Sensor First off, the sensor. This is a light-dependent resistor, or LDR aka photoresistor: a little…