miniblog.

I've been experimenting with an 'evaluate up to cursor' mode for my PL project. I love evaluating self-contained snippets in Lisp, this generalises the idea. The interpreter remembers the arguments when you run tests, then can re-use them when you say 'eval up to here'. What do you think?

I'm having fun writing a simple type checker, but I'm learning firsthand why syntax-directed checking doesn't work. It prevents inference. My checker catches real bugs, but it can't handle cases like this: [1, 2].map(fun(x) { x + 1; }) I think I need bidirectional checking.

I regularly see the phrase "all Xs are Ys, but not all Ys are Xs" in teaching material. Even material for children! I have to re-read it every time. I very much prefer "Y is a more general category than X" or "X is a subset of Y". Do people find this phrasing helpful, or is it poor pedagogy?