abyss-rs

Rust implementation of Abyss programming language

Getting started

• Download or compile source code.
• Run the program and enter repl automatically (default lazy mode).

REPL functions

• quit: Quit repl
• help: Get help
• eager: Turn on eager mode (where strict evaluation is the default)
• lazy: Turn on lazy mode (where lazy evaluation is the default)
• debug: Turn on debug mode

Expressions

• Function application: (f x)
• Let bindings: (let ((x value) (y value) ...) expression)
• Lambda abstraction: (lambda (x y z ...) expression)
• If branches: (if expression true-branch false-branch)
• Pattern matching: (case expression ((case1 value) (case2 value) ...))

Declarations

• Definition: (define x expression) | (define (f x y ...) expression)
• Data abstraction: (data x) | (data (cons x y ..))

Environment

• Integers
• Symbols
• Strings
• Real numbers
• ::: List constructor
• +-*/: Arithmetic operators

Features

• Typed dynamic programming language
• Highly configurable and scalable
• Experimental for the next generation

Expressions

• S-Expressions
• Scalable front-end syntax with parser combinator

Evaluation

• Optional evaluation strategy: eager or lazy
• Flexible GC strategy

Data abstraction

• Haskell-like data declaration
• Pattern matching everywhere

Type system

• Dependent type system

Examples

• Factorial

(let (((fact n) (case n ((0 1) (n (* n (fact (- n 1)))))))) (fact 5))
;==> 120

• Generating list

(let (((gen s n) (case n ((0 ()) (n (:: s (gen s (- n 1)))))))) (gen 'T_T 10))
; strict ==> (T_T T_T T_T T_T T_T T_T T_T T_T T_T T_T)
; lazy   ==> (:: T_T <thunk>)