Brian McKenna’s “Row Polymorphism Isn’t Subtyping” is about the distinction between row polymorphism and subtyping. Several re-readings led me to convince myself I understood, then a real-world bug to lead me to a stronger conclusion on why the distinction matters. To help cement my understanding or misunderstanding, I’ll Say more…

There’s normally a tight connection between programming and proving: this is known as “Propositions as Types.” I found one aspect of the correspondence troubling, went down a rabbit hole, and came back less troubled. Our most popular logical systems all include exfalso, a.k.a. The Principle of Explosion which is the…

There are many places where you can find arguments that DSLs (domain-specific languages) or “language oriented programming” are good. But I haven’t found much on what makes them bad. My experiences with DSLs tend to be negative. There are cases where I know exactly what I want the computer to…

I’ll present four puzzles and two solutions about classes and types. These are just puzzles I find fun, but reading this might have the happy side effect of getting you out of a TypeScript jam in the future. …

TypeScript, like many programming languages provides enums, which enable you to enumerate the values a type may have. TS enums look like this: enum Direction { UP, DOWN } function move(direction: Direction) {} move(Direction.UP); I’ll go into: Alternatives to enums: string unions and object literals How enum is terrible Note…

Here are two tables that show the similarities and differences between MobX Observables and Rx Observables: Similarities Differences ALSO:

There are a ton of libraries for doing asynchronous effects in Redux apps. Some see this as a bad thing, but I love the intellectual curiosity and willingness to explore in the JavaScript community. There wasn’t a Redux effects library that met my needs, so I ended up making something…

I’ve noticed that Redux apps often embed ad-hoc finite state machines, with information about the current status spread out throughout reducers. I wrote a small helper for working with finite state machines in Redux called redux-machine. In this post, I’ll go into: An example of a finite state machine and…

I’ll go into: Traditional Monkey Patching and why it is Dangerous Safe Monkey Patching with Symbol and chill-patch Safe Monkey Patching in other Languages Why the Pipeline Operator Proposal is Great Traditional Monkey Patching and why it is Dangerous “Monkey patching” in JavaScript refers to adding properties to a prototype separately from where the class is first defined…