The Lisp in the Cellar: Dependent types that live upstairs [pdf]
23 comments
·May 20, 2025droideqa
Sadly "deputy clojure" on Google brings no results...
The only hint is this repo[0] referenced in the paper.
agumonkey
Pretty readable code
reuben364
Thinking out aloud here.
One pattern that I have frequently used in EMACS elisp is that redefining a top-level value overwrites that value rather than shadowing it. Basically hot reloading. This doesn't work in a dependently typed context as the type of subsequent definitions can depend on values of earlier definitions.
def t := string
def x: t := "asdf"
redef t := int
Excluding the type-level debugging they mention, I think a lean style language-server is a better approach. Otherwise you are basically using an append-only ed to edit your environment rather than a vi.
wk_end
I've fantasized about some kind of a dependently-typed Smalltalk-like thing before, and in those fantasies the solution would be that changes would be submitted in the form of transactions - they wouldn't be live until you bundled them all together into one big change that would be fully type-checked, as you describe.
kscarlet
The only option that you described is called "hyperstatic global environment".
And it is called that for a reason, it is not very dynamic :) and probably too static to the taste of many Lisp and all Smalltalk fans.
resize2996
> EMACS elisp
I used this to write the front end for an ATM machine.
extrabajs
I don’t see the connection to dependent types. But anyway, is ‘redef’ part of your language? What type would you give it?
reuben364
I just wrote redef to emphasize that I'm not shadowing the original definition.
def a := 1
def f x := a * x
-- at this point f 1 evaluates to 1
redef a := 2
-- at this point f 1 evaluates to 2
extrabajs
I see what you mean. But would you not experience the same sort of issue simply from redefining types in the same way? It seems this kind of destructive operation (whether on types or terms) is the issue. As someone who's used to ML, it seems strange to allow this kind of thing (instead of simply shadowing), but maybe it's a Lisp thing?
fithisux
Impressive.
reikonomusha
Related context: The 2025 European Lisp Symposium [1] was just wrapped a few hours ago in Zurich. There was content on:
- Static typing a la Haskell with Coalton in Common Lisp
- Dependent typing with Deputy in Clojure (this post)
- The Common Lisp compiler SBCL ported to the Nintendo Switch
- Common Lisp and AI/deep learning
- A special retrospective on Modula and Oberon
- Many lightning talks.
no_wizard
I feel like Lisp would be an ideal language for AI development. Its exceedingly good for DSL development and pattern matching. Its already structurally like math notation as well, which I would think would lend itself to thinking how models would consume information and learn
rscho
Well... believe it or not, some have thought of using lisp for AI for quite some time. ;-)
ayrtondesozzla
https://quantumzeitgeist.com/lisp-and-the-dawn-of-artificial...
Lisp was the de facto language of artificial intelligence in the U.S. for many years. Apparently Prolog was popular in Europe (according to Norvig's PAIP)
froh
indeed.
Peter Norvig, 1992
Paradigms of AI Programming: Case Studies in Common Lisp
https://en.m.wikipedia.org/wiki/Peter_Norvig
it's no coincidence Google is actively maintaining sbcl, either.
Zambyte
Why not go all the way to the source? John McCarthy coined the term "artificial intelligence", and then invented / discovered LISP in pursuit of it in the 1950s :D
null
dang
Any URL for this that we can open in a browser (as opposed to the dreaded "Content-Disposition: attachment")?
Jtsummers
https://zenodo.org/records/15424968 - This at least takes you to a webpage where you can view the paper. If you select to download it, it still downloads of course instead of just opening in the browser.
dang
Thanks! I've switched to that above, and put the downloadable link in the top text.
sfpityparty
[flagged]
Downloadable: https://zenodo.org/records/15424968/files/deputy-els.pdf