Risp
Risp is a LISP implementation written in Ruby. The syntax is reminescent of
Clojure, and it interoperates with Ruby.
Why?
Why not? :P
Mostly I did this to learn a bit more about programming language design. Or maybe I was bored. And also I really like LISPs and I like the idea of writing LISP leveraging on the Ruby ecosystem. But still this is mostly an experiment, so if you use it you cannot blame me if it ends up eating your laundry or setting your kitchen on fire.
Installation
$ gem install risp-lang
Usage
Start a REPL
Just run risp-repl
Execute a file
risp my_program.risp
Inside Ruby
Instantiate an interpreter and evaluate code:
require 'risp'
risp = Risp::Interpreter.new
risp.eval <<-CODE
(def double [x]
(* 2 x))
(double 5)
CODESyntax
The LISP syntax is very similar to Clojure:
; Define a function
(defn dec [n]
(- n 1))
; Define recursive factorial
(defn fact [n]
(if (<= n 1)
1
(* n (fact (dec n)))))
(fact 10) ; => 3628800
; Rest argument
(defn foo [a b &more]
[a b more])
(foo 1 2 3 4 5) ; => [1 2 [3 4 5]]
; Argument destructuring
(defn swap-pairs [[a b] [c d]]
[[a c] [b d]])
(swap-pairs [1 2] [3 4]) ; => [[1 3] [2 4]]Macro support
Macros, quoting and unquoting are supported:
(defmacro defn- [name args body]
'(def ~name (fn ~args ~body)))
(defn- sum [a b]
(+ a b))
(sum 4 5)Ruby interoperability
; Ruby methods can be called the same way as LISP functions, just prepend a
; dot to the method name, pass the receiver as the first argument, followed
; by any other argument:
(.join ["highway" "to" "the" "danger" "zone"] " ")
; Ruby constants, modules and classes are available, just use Foo/Bar instead
; of Foo::Bar:
(defn circle-area [radius]
(* Math/PI radius radius))Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/lucaong/risp.
License
The gem is available as open source under the terms of the MIT License.