SPLV20
pie
SPLV20 | pie | |
---|---|---|
1 | 10 | |
102 | 671 | |
- | 0.4% | |
10.0 | 10.0 | |
over 1 year ago | almost 3 years ago | |
Idris | Racket | |
- | GNU Affero General Public License v3.0 |
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SPLV20
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The Little Typer – The Beauty of Dependent Type Systems, One Step at a Time
Internally, the Idris2 compiler uses deBruijn numbering for its terms, which is tricky to get right once you start trying to manipulate terms. To help with this, it keeps a list of the names corresponding to the deBruijn indices at the type level. The type checker catches mistakes as you write code to manipulate them (inserting names, removing names, or renaming things).
I ran through some exercises teaching this technique[1]. My take-away as a beginner was that it was a pain to make the compiler happy and my code that the compiler didn't like was actually wrong.
I remember reading someone had written a functional red-black tree (with proof of correctness leveraging dependent types) and said the delete algorithm naturally followed from the types. That has was not my experience (delete wasn't immediately obvious to me), but I need to find some time to give it another go.
The Idris2 docs have an example of a lambda expression interpreter[2] whose terms have a vector of the types in the environment as a type parameter (erased at runtime), to ensure everything is type safe in the resulting interpreter.
Typescript has added some bits of dependent typing. For example, asserting a function returns true if the argument has type X, that a function throws if the argument is falsy, and I think type level string manipulation. They are fairly pragmatic, it's not a research language, so I presume that specific functionality is useful to a lot of people. I've used it a little bit of it to help the type checker infer non-null after my assert function was called.
All of that said, I think people are still exploring how dependent types can be used in practice.
[1]: https://github.com/edwinb/SPLV20/blob/master/Code/Lecture2/E...
pie
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Can DSLs in Racket be its own language?
Pie, a dependently typed language for learning dependently typed programming
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is CS an engineering practice?
The computer scientists who are figuring these things out are constructing the tools that software engineers need; just like the mathematicians who developed calculus and the physicists who extended Newtonian mechanics into something engineers can apply. Just as an engineer's tools and materials are calculus and physics (not hammers or concrete and steel), a software engineer's tools and materials are proof-assistants, category theory, linear polarized logic, and dependent type theory (not the Rust programming language or the UNIX platform).
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Carp – a statically typed, non-GC Lisp language
That's basically this[0] book, is it not?
[0] https://thelittletyper.com
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Is Lisp particularly suitable for sole developer or small teams?
I really should read https://thelittletyper.com/
- The Little Typer – The Beauty of Dependent Type Systems, One Step at a Time
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RacketCon 2022
It lets you create languages like Pie which is designed to teach others about dependent types:
https://thelittletyper.com/
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Honest question: why is Haskell not a lisp / built on s-expressions?
Yep, this is one possibility - an example is the language pie from the book The Little Typer. But my claim was not that there are no expressions for types, just that declarations aren't expressions.
What are some alternatives?
ATS-Postiats - ATS2: Unleashing the Potentials of Types and Templates
hackett - WIP implementation of a Haskell-like Lisp in Racket
Idris - Codes related to Idris
Summer2022 - Lang Party 2022
anarki - Community-managed fork of the Arc dialect of Lisp; for commit privileges submit a pull request.
minipascal - MiniPascal implemented in Racket
structured-haskell-mode - Structured editing minor mode for Haskell in Emacs
slite - a SLIme-based TEst runner for FiveAM and Parachute Tests
Folly - An open-source C++ library developed and used at Facebook.
stalin - stalin brutally optimizing Scheme compiler, with Debianization patches