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# 🧚 puck - an experimental programming language
A place where I can make some bad decisions.
Puck is an experimental, memory safe, structurally typed, imperative and functional programming language.
It aims to be clean and succinct while performant: having the flexibility/metaprogramming of [Nim](https://nim-lang.org/) with the error handling of [Swift](https://www.swift.org/) and the performance/safety guarantees of [Rust](https://www.rust-lang.org/).
You may judge for yourself if Puck meets these ideals.
```nim
import std/tables
module AST:
pub type Value = interface
func repr(self: Self): string
pub type Ident = string
pub type Expr = ref union
Literal: Value
Variable: Ident
Abstraction: struct[param: Ident, body: Expr]
Application: struct[body, arg: Expr]
Conditional: struct
cond, then_case, else_case: Expr
pub func eval(expr: Expr, context: var HashTable[Ident, ref Value]): Result[ref Value]
match expr
of Literal(value):
Okay(value)
of Variable(ident):
context.get(ident)
of Application{body, arg}:
if body of Abstraction{param, body as inner_body}:
context.set(param, eval(arg))
inner_body.eval(context)
else:
Error(InvalidExpr)
of Conditional{cond, then_case, else_case}:
if eval(cond, context):
then_case.eval(context)
else:
else_case.eval(context)
of _:
Error(InvalidExpr)
AST.eval((λx.x) 413)
```
## Why Puck?
Puck is primarily a testing ground and should not be used in any important capacity.
Don't use it. Everything is unimplemented and it will break underneath your feet.
That said: in the future, once somewhat stabilized, reasons why you *would* use it would be for:
- The **syntax**, aiming to be flexible, predictable, and succinct, through the use of *uniform function call syntax* and significant whitespace
- The **type system**, being modern and powerful with a strong emphasis on safety, optional and result types, algebraic data types, and interfaces
- The **memory management system**, implementing a model of strict ownership while allowing individual fallbacks to reference counts if so desired
- The **metaprogramming**, providing flexible integrated macros capable of rewriting the abstract syntax tree before or after typechecking
- The **interop system**, allowing foreign functions to be usable with native semantics from a bevy of popular languages
<!-- - The **effect system**, being one of few languages with a proper effects system based on handlers -->
This is the language I keep in my head. It sprung from a series of unstructured notes I kept on language design, that finally became something more comprehensive in early 2023. The overarching goal is to provide a language capable of elegantly expressing any problem, and explore ownership and interop along the way.
## How do I learn more?
- The [basic usage](docs/BASIC.md) document lays out the fundamental semantics of Puck.
- The [syntax](docs/SYNTAX.md) document provides a deeper and formal look into the grammar of Puck.
- The [type system](docs/TYPES.md) document gives an in-depth analysis of Puck's extensive type system. <!-- and its relationship to classes and other abstractions. -->
- The [memory management](docs/MEMORY_MANAGEMENT.md) document gives an overview of Puck's memory model. <!-- which is considered a mashup of the models pioneered by Lobster, Rust, and Nim. -->
- The [metaprogramming](docs/METAPROGRAMMING.md) document explains how using metaprogramming to extend the language works. <!-- and write more powerful code works. -->
- The [asynchronous](docs/ASYNC.md) document gives an overview of the intertwining of Puck's asynchronous support with other language features.
- The [interop](docs/INTEROP.md) document gives an overview of how the first-class language interop system works.
- The [modules](docs/MODULES.md) document provides a more detailed look at imports and how they relate to the type system.
<!-- - The [effect system](docs/EFFECTS.md) document gives a description of how Puck's effect handler system works. -->
- The [standard library](docs/STDLIB.md) document provides an overview and examples of usage of the standard library.
- The [roadmap](docs/ROADMAP.md) provides a clear view of the current state and future plans of the language's development.
These are best read in order.
Note that all of these documents (and parts of this README) are written as if everything already exists. Nothing already exists! You can see the [roadmap](docs/ROADMAP.md) for an actual sense as to the state of the language. I simply found writing in the present tense to be an easier way to collect my thoughts.
## Acknowledgements
First and foremost, this language is *heavily* inspired by Nim. Many ideas - general syntax, UFCS, even the design of the compiler - were taken 1:1.
The error handling model, and purity system, were essentially directly lifted from Swift (and to an extent, Nim).
The underlying type system is mostly copied from Rust, with significant changes to the interface (trait) and module system.
The memory model is based upon similar successful models in Lobster, Nim, and Rust. Performance annotations are somewhat inspired by Nim.
<!-- The effects system is unique, with inspiration from the few languages successfully implementing effects systems, namely Koka and Unison. -->
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