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https://github.com/divs1210/predscript
Predicates as Types. Compiles to JS.
https://github.com/divs1210/predscript
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Predicates as Types. Compiles to JS.
- Host: GitHub
- URL: https://github.com/divs1210/predscript
- Owner: divs1210
- License: mit
- Created: 2023-09-18T13:39:27.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-03-21T21:44:39.000Z (8 months ago)
- Last Synced: 2024-03-22T20:38:39.189Z (8 months ago)
- Language: JavaScript
- Size: 164 KB
- Stars: 4
- Watchers: 2
- Forks: 0
- Open Issues: 12
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
[](https://opensource.org/licenses/MIT) 
# PredScript
## What
PredScript is a functional programming language with first-class types.
### Features
- [functional and data driven language](/examples/collections.ps)
- [functions are polymorphic and dispatch on types of all arguments](/examples/math.ps)
- [types are arbitrary functions that return booleans (predicates)](/examples/poly.ps)
- [types can have subtypes](/examples/hierarchy.ps)
**!! BEWARE: WIP !!**
## Why
If a language's type system was built around predicates -
abitrary functions of one argument that return booleans -
we could define types like `isPositiveInt`, `isEmailString` etc.
In the statically typed world, these kind of types are called [dependent types](https://en.wikipedia.org/wiki/Dependent_type).
Dependently typed languages like [Agda](https://github.com/agda/agda), [Idris](https://github.com/idris-lang/Idris2), etc.
often involve writing a lot of proofs which makes them not very well
suited for general purpose programming.
PredScript is an attempt to make a flexible dependently-typed functional language
with familiar (easy / mainstream / JS-like) syntax that lies
somewhere on the spectrum of `Dynamically Typed → Statically Typed`.
## Code Example
```typescript
interface isEmailString extends isString;
function isEmailString(s: isString): isBool {
/^\S+@\S+\.\S+$/
.test($this, s)
}
let isUser: isPred = gen_isRecord({
"id": isInt,
"username": isString,
"email": isEmailString
});
let u: isUser = as(isUser, {
"id": 1,
"username": "johndoe",
"email": "[email protected]"
});
```
## Design goals
- Types can be arbitrary predicates (like `isEmailString` and `isPositiveInt`)
- Be amenable to static type checking / type linting
- Dynamically type check at runtime
- do it efficiently
- runtime can be directed to skip arbitrary checks (for optimization)
- Polymorphic
- Compile to JS
- Interop with JS
- Look and feel similar to JS
## Usage
### Install
PredScript is developed against `node 20.6.1`.
Use [nvm](https://github.com/nvm-sh/nvm) to install it.
```shell
$ nvm install 20.6.1
$ nvm use 20.6.1
```
Download and install PredScript
```shell
$ git clone https://github.com/divs1210/PredScript
$ cd PredScript
$ npm i
```
### Compile and run [examples](/examples/poly.ps)
```shell
$ node compile.js examples/poly.ps
$ node dist/index.js
```
### Run tests
```shell
$ npm test
```
## License
[MIT License](/LICENSE)
(C) Divyansh Prakash, 2023-2024