crisp

A simple, securable, embeddable lisp interpreter for rust programs.

Status

Incredibly pre-alpha, is not fully implemented, doesn't work yet.

Examples

(defn fac [n]
  (if (< n 2)
    1
    (n * (fac (- n 1)))))
(defn sum [... ns]
  (apply + ns))

Design

Crisp is initially designed to be a simple interpreter.

Vexes

Fexprs are a first-class alternative to macros. The idea is quite simple, they're like functions that take their arguments unevaluated and the calling environment. They can choose to evaluate their arguments in the calling environment or not.

Fexprs were conceived fairly early on but didn't really stick because dynamic scope was the predominant paradigm of the day. These days the dominant paradigm is lexical scope and it turns out they work quite well.

Fexprs are more powerful than macros and remove both the macroexpansion step and the need for hygiene (we have lexical scope, which is better!). Because there is no generating code per se, code always has a direct correspondence to what was typed.

Notes

Built-in primitives:

• fx - create an anonymos f-expression
• fn - create an anonymos function
• define - define a value in the current module
• defx - define an f-expression in the current module
• defn - define a function in the current module
• spawn - start a new greenthread

Copyright and License

Copyright (c) 2021 James Laver, crisp contributors

Licensed under Apache License, Version 2.0 (https://www.apache.org/licenses/LICENSE-2.0), with LLVM Exceptions (https://spdx.org/licenses/LLVM-exception.html).

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be licensed as above, without any additional terms or conditions.