Having written a PhD thesis, however, I know all too well that feeling productive and actually being productive are things that don't always correlate. After digging through my notes and my Github commits I managed to compile this (non-exhaustive) list of stuff I did since my last post:

- I made sure 'weird' expressions such as p^y_a^z'_b compile to sensible MathML code. LaTeX will actually give you an error if you type that; Termcat interprets it as p^{yz}'_{ab}. Incidentally, the MathML for that is <msubsup><mi>p</mi><mrow><mo>{</mo><mi>a</mi><mi>b</mi><mo>}</mo></mrow><mrow><mo>{</mo><mi>y</mi><mi>z</mi><mo>}</mo><mo>′</mo></mrow></msubsup>. Talk about verbose!
- I ripped out some features that were dear to me, such as the ability to use '<' and '>' to delimit tuples. This, I realized, was confusing in many contexts. (One feature I did keep is that the Termcat code <~ ... ~> converts the delimiters to proper chevron glyphs.)
- I made many parsing rules a lot stricter. This means there's less chance of accidentally triggering special Termcat features.
- I improved the typography of Termcat documents.
- I experimented with syntax for bound names and for lambdas.
- I read up on finite state automata (which are used to match regular expressions) and finite state transducers (which can do substitutions). One outcome of this is the conjecture that if I change the semantics of my rewriting system somewhat then my rewriting rules may become composable. This means that instead of having to do a pass over all tokens for every rule, it may be possible to automatically combine all rules first and then run them all at once in a single pass. I already alluded to this in an earlier blog post and I might do some work on this this week.