A Scheme Implementation using Pa_schemer from Camlp5

This repository contains a scheme implementation based on pa_schemer.ml which is included as an extension of camlp5. This provides a scheme-like syntax for OCaml. The camlp5 documentation for the scheme extension provides the following comparison between OCaml and scheme syntax:

OCaml	Scheme
let x = 42;;	(define x 42)
let f x = 0;;	(define (f x) 0)
let rec f x y = 0;;	(definerec (f x y) 0)
let x = 42 and y = 27 in x + y;;	(let ((x 42) (y 27)) (+ x y))
let x = 42 in let y = 27 in x + y;;	(let* ((x 42) (y 27)) (+ x y))
module M = struct ... end;;	(module M (struct ...))
type 'a t = A of 'a * int | B	(type (t 'a) (sum (A 'a int) (B)))
fun x y -> x	(lambda (x y) x)
x; y; z	(begin x y z)
f x y	(f x y)
[1; 2; 3]	[1 2 3]
a, b, c	(values a b c)
match x with 'A'..'Z' -> "x"	(match x ((range 'A' 'Z') "x")))
{x = y; z = t}	{(x y) (z t)}

p5scm also provides the following:

OCaml	Scheme
[|1; 2; 3|]	#(1 2 3)

which is provided via a simple menhir parser that supports all of the syntax above.

Installation

As long as you have a current version of opam, installation is as simple as:

$ opam install p5scm

You can then use it to parse and emit OCaml bytecode that can then be used in your OCaml project:

$ p5scm file1.scm

You can also start an interpreter for p5scm:

$ p5sch-utop

which uses utop for code completion and many of the other benefits that it provides. Currently both the #require and #use directives of utop function in the interpreter/REPL (same syntax as utop however no terminating ;; required).

Only OCaml versions >= 4.12.0 are supported by the opam package. Instructions for adding support for older versions can be found (here).

License

MIT