Hacker News Reader

Comment by pfdietz | Hacker News Reader

> is often interpreted

Every competitive Common Lisp implementation has compilation. SBCL defaults to not even using an interpreter for eval.

And CCL doesn't even have an interpreter. Every form you type into the REPL is compiled. If you want an interpreter in CCL you have to write it yourself.

worth mentioning is that CCL is finally back into active development !

Who is doing the development currently?

Matthew Emerson

https://lists.clozure.com/pipermail/openmcl-devel/2024-April...

SBCL eval interprets until you hit a lambda form, at which point it will compile (last I checked). But you are much more correct than who you replied to :)

Unless I'm misremembering, this is only true in REPL, which should be better read as "SBCL is actually sometimes *AoT-compiling in interactive REPL sessions!!!"; #'LOAD-ing files would AoT-compile them by default.

This is reminding me there is the sb-fasteval feature, which I have not been testing.

It didn't use to - for various reasons, evaluator inherited from CMU CL had bitrotted at one point, and for many years every form more complex than essentially single function call resulted in compilation.

Few years ago there was work to fix the evaluator and now EVAL has limited evaluation back.

I thought SBCL was a compiler only implementation? CMUCL did have an interpreter though.

It was until someone resurrected the evaluator it inherited from CMUCL

CMUCL's interpreter evaluated IR1 (the first intermediate representation of its compiler) IIRC, so it wasn't possible to have a truly compilerless CMUCL _and_ a functional EVAL. I believe this IR1 interpreter was dropped from SBCL very early on. When SBCL gained an interpreter again it was a simple metacircular evaluator a la SICP that was unrelated to anything inherited from CMUCL. (This is all as of 15 or so years ago, I'm sure things have evolved since then!)

SBCL has two evaluators now, sb-eval and sb-fasteval. I don't know how much structure they share. By default it builds with sb-eval, but this can be changed with options to make.sh. sb-ext:*evaluator-mode* is still :compile by default.

Reply on news.ycombinator.com