Monday, March 06, 2006

Redex is cool

I hadn't looked at PLT Redex since its pre-publication days, but yesterday I started using it to implement my draft model for Topsl, the programming language for implementing online surveys. I couldn't believe how easy it was! I expected it to take quite a while, but within an hour I had a working operational model of core Scheme, and half an hour later I had the entire grammar of Topsl and even a few nice abstractions. I haven't quite finished the implementation yet, but it's been surprisingly painless.

Of course, it helps to have a good understanding of macrological* pattern-matching and template instantiation, capture-avoiding substitution, and Felleisen-style context-sensitive reduction semantics, so you might say I'm uniquely suited to use the tool. Regardless, I'm very impressed.

* This is a very silly adjective. Please don't ever use it. Someone could get hurt.


Sam TH said...

Wait, I thought the PLT-Redex pattern matching was, rather than macrological.

And yes, I wrote this comment just to use the word "macrological".

Dave Herman said...

It uses, yes, but I meant that it uses a macrological (cough) style. The "term" form is like "syntax", and redex has automatic template variable substitution that's more like syntax-rules than unquoting.

Robby said...

I just came across this, but I wanted to point out that redex's pattern matcher uses to parse the patterns (for the purpose of compiling them), but that's it. The pattern matcher itself is different than's; it produces all possible matches for things with, say, repeated ellipses. Plus, it draws from grammars that might be ambiguous, etc.