Today I updated a library version in a project, which changed the path from packages/FSharp.Formatting.CommandTool-2.8.0 to packages/FSharpFormatting.CommandTool-2.9.1. We’d also taken our own copies of some templates in the package, and I wanted to check if there were any differences between -2.8.0\templates and -2.9.1\templates that I should port across.

Rather than my usual fumbling about (check out both, copy, diff) I thought I’d try to learn the necessary Git incantation to compare the paths. And then blog it, so that when I forget I’ll have a quick reference handy for next time. :)

Today I was speaking with a colleague about some F#, and he pointed out a few gotchas with F# type signatures, especially if you’ve spent some time with Haskell (and not OCaml or other ML-ish language).

F# gave me the following error when working with some C# code:

error FS0729: This field is not a literal and cannot be used in a pattern 

I’m not entirely sure it’s a good idea, but I managed to work around this using a partial active pattern.

I’ve been trying to learn D3.js via Mike Bostock’s excellent “Let’s make a bar chart” tutorial series. This post is my attempt to extend that example to handle data updates.

I recently had loads of fun attending a Nodebots AU event in Sydney. (Thanks a lot to Damon and Andrew for organising, and NICTA for the venue!) I got to muck around with some simple circuits and drive them with Javascript. Towards the end of the day I was running out of time and creativity to do anything fancy, so I decided to see if I could get one of the circuits working with Haskell.

There are a few different libraries that provide test assertions for F#. I went through a couple today and tried a trivial example in each.

Every so often I want to quickly sketch out what should be a simple diagram. Irrespective of what drawing program I use, I always seem to take much more time than I intend for a result that does not even remotely resemble what I want.

So I decided to give up and find a way to use hand-drawn sketches instead. Here’s the method I ended up with, based almost entirely on Marc Liberatore’s “Whiteboard Diagrams as PDFs” post and the wonderful ImageMagick and Potrace utilities.

My drawings still look fairly terrible, but at least they convey what I want them to and are quick to produce! :)

Apparently it can be a bit tricky to get some Haskell libraries working on Windows, in which case the Haskell Platform is a great way to get going with Haskell. For Mac and Linux the platform works too, but we can also just grab the latest GHC and Cabal (ooh, shiny!) and go from there.

UPDATE 2019-02: I tend to use ghcup on Mac and Linux these days. Am leaving these steps here as building GHC and Cabal is still a valid way of getting Haskell up and running.

tl;dr: Make invalid regular expression strings and attempts to access non-existent capture groups a compile-time error, thanks to the Regex type provider.