Are there any good starting places for learning the necessary type theory to understand this stuff? I really like the idea of extensible row types, but struggle with trying to understand the research papers.
Types and Programming Languages by Pierce. Available online if you search for it. Expresso appears to be, more or less, an extension of the toy language implemented in that book.
This looks pretty cool. It's nice to have an open source Rust game. Getting started developing a game in Rust is a bit rough, so having a reference like this is very helpful.
Yes, this seems to be the right behavior for case-insensitive things like DNS names as well. If a user inputs one, preserve the case when you store it, but do case-insensitive comparisons.
If I remember right, TAPL (Types and Programming Languages by Benjamin Pierce) contains implementations for nearly everything that it talks about. So you can find another implementation of Hindley-Milner there.
Does anyone know of a similar tool for XML? In particular, it would be cool to have a useful way to run xpath, and maybe xquery, from the command line. The tools I've found have unfortunate interfaces, e.g. they won't read XML from stdin.
Most of the JSON conversions from XML get it all wrong though. XML is not really an object (dict, hash) based meta-schema. It's an array-based meta-schema. XML->JSON conversions should look something like this:
I am not a huge fan of PHP, but you can do some useful stuff to XML using the PHP command line tool, provided you have the right libraries installed. I have run into situations where the package manager on a machine I'm using doesn't have an up to date xmlstartlet or xmllint, and have tidily gotten around this problem using PHP.
