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73 lines
2.8 KiB
Markdown
73 lines
2.8 KiB
Markdown
Kind2
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=====
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Kind2 is a pure functional, lazy, non-garbage-collected, general-purpose,
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dependently typed programming language focusing on performance and usability. It
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features a blazingly fast type-checker based on **optimal
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[normalization-by-evaluation](https://en.wikipedia.org/wiki/Normalisation_by_evaluation)**. It can also
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compile programs to [HVM](https://github.com/kindelia/hvm) and [Kindelia](https://github.com/kindelia/kindelia),
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and can be used to prove and verify mathematical theorems.
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Examples
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--------
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Pure functions can be defined using an equational notation that resembles [Haskell](https://www.haskell.org/):
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```idris
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List.map <a: Type> <b: Type> (x: (List a)) (f: (x: a) b) : (List b)
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List.map a b (Nil t) f = (Nil b)
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List.map a b (Cons t x xs) f = (Cons b (f x) (List.map xs f))
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```
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Mathematical theorems can be proved via inductive reasoning, as in [Idris](https://www.idris-lang.org/) and [Agda](https://wiki.portal.chalmers.se/agda/pmwiki.php):
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```idris
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Nat.commutes (a: Nat) (b: Nat) : (Nat.add a b) == (Nat.add b a)
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Nat.commutes Zero b = (Nat.comm.a b)
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Nat.commutes (Succ a) b =
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let e0 = (Equal.apply @x(Succ x) (Nat.commutes a b))
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let e1 = (Equal.mirror (Nat.commutes.b b a))
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(Equal.chain e0 e1)
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```
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Normal programs can be written in a monadic syntax that is inspired by [Rust](https://www.rust-lang.org/) and [TypeScript](https://www.typescriptlang.org/):
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```idris
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Main : (IO (Result () String)) {
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ask limit = (IO.prompt "Enter limit:")
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for x in (List.range limit) {
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(IO.print "{} * 2 = {}" x (Nat.double x))
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}
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return (Ok ())
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}
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```
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For more examples, check the [Wikind](https://github.com/kindelia/wikind).
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Installation
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------------
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Install [Rust](https://www.rust-lang.org/tools/install) first, then enter:
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```
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cargo install kind2
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```
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Enter `kind2` on the terminal to make sure it worked.
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Usage
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-----
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Command | Usage | Note
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---------- | ------------------------- | --------------------------------------------------------------
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Check | `kind2 check file.kind2` | Checks all definitions.
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Eval | `kind2 eval file.kind2` | Runs using the type-checker's evaluator.
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Run | `kind2 run file.kind2` | Runs using HVM's evaluator, on Rust-mode.
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To-HVM | `kind2 to-hvm file.kind2` | Generates a [.hvm](https://github.com/kindelia/hvm) file. Can then be compiled to C.
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To-KDL | `kind2 to-kdl file.kind2` | Generates a [.kdl](https://github.com/kindelia/kindelia) file. Can then be deployed to Kindelia.
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Benchmarks
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----------
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In preliminary [benchmarks](/bench), Kind2's type-checker has outperformed Agda, Idris by 90x to 900x, which is an expressive difference. That said, we only tested a few small programs, so there isn't enough data to draw a conclusion yet. We're working on a more extensive benchmark suite.
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