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Ralph

Ralph is a Lisp-1 dialect that compiles to JavaScript. It is heavily inspired by an early version of Dylan (also known as "Prefix Dylan"), as described in Dylan – An object-oriented dynamic language.

Getting started

Installation

First, install Node.js and then all necessary modules:

  • $ npm install

The directory core already contains the full Ralph runtime and compiler as pre-compiled JavaScript, so you are ready to go.

REPL

To start a local, Node.js-based REPL, run:

  • $ NODE_PATH=core node repl.js

To start a remote, browser-based REPL, install browserify, generate the browser evaluator, start the REPL with the --remote option, and open index.html in your browser:

  • $ NODE_PATH=~/node_modules:core browserify evaluator.js -o evaluator.out.js
  • $ NODE_PATH=core node repl.js --remote

Compilation

To compile a simple "Hello, world!" program:

  • Place hello.ralph into src:

    (define-module hello
  import: (ralph/format-out)
  export: (hello))
    
(define-function hello (name)
  (format-out "Hello, %s!" name))

  • Compile the hello module. The compiler outputs files into build.

    $ NODE_PATH=core node -e "require('ralph/compiler')['compile-module']('hello')"

  • Run the program by opening the hello module and calling the hello function:

    $ NODE_PATH=build node -e "require('hello')['hello']('World')"
Hello, World!

Documentation

There is unfortunately no API documentation. The module ralph/core contains the core runtime and the standard library.

The manual of Prefix Dylan can be used as a reference and is a good introduction into the language.

There are also slides from a talk given at ILC 2012, and a paper explaining the motivation, features and compilation strategy of Ralph.

Syntax

For performance reasons, Ralph is using JavaScript arrays as its core data structure, instead of implementing its own list data structure based on objects. Arrays can be created using the [] syntax (e.g. (first [1 2 3])).

The syntax for numbers and strings is that of JavaScript.

Symbols may contain any character which is not otherwise syntactically significant (e.g., introduces a number, an array, etc). The character sequence :: in symbols is treated as the separator for fully-qualified symbols: The first part is the module name, the second is the symbol name.

Keywords have the same syntax as symbols and end with a colon (e.g., foo:).

The syntax for the canonical true value is #t, for the canonical false value #f.

In parameter lists, #rest is used to introduce the name of the variable containing the additional arguments, and #key is used to introduce keyword parameters.

A single quote is used for quoting. A backquote is used for syntax-quoting (see macros).

A semicolon indicates the start of a comment.

Interoperability

The special operator %native allows writing inline JavaScript. All strings that are passed to it are directly emitted as-is. Numbers are first converted to strings, and symbols are properly renamed. Other forms are not supported.

For example, the following Ralph code

(bind ((delta 3))
  (%native "x += " delta " * " 2))

would compile to the following JavaScript code:

var delta__1 = 3;
x += delta__1 * 2;

Ralph's compiler knows nothing about the global x and there is no need to declare it exists.

The utility macro . can be used for easily writing JavaScript method calls. For example,

(. (%native "console") 
   (log "Hello, %s" "World"))

would compile to:

console.log("Hello, %s!", "World");

Ralph also integrates well with Node.js. To be able to use a Node.js module in Ralph, place a .rm file (ralph module definition) in src that specifies the name, it is native (native?: #t) and the definitions it is exporting.

For example, a basic definition for the Node.js module vm could look like:

("vm"
 native?: #t
 exports: ("createContext" "runInContext"))

See fs and ralph/file-system for a an extended example of this mechanism.

Macros

Ralph supports hygienic macros through Clojure-like syntax-quoting.

In a separate module, define the macro using define-macro. In the module you want to use it, import the module during compilation using the compile-time-import: option in the define-module definition.

For a full example, see ralph/macro-test.a, which can be compiled using.

$ NODE_PATH=core:build node -e "require('ralph/compiler')['compile-module']('ralph/macro-test.a')"

The section "Macro system" in the paper contains more details.

Development

The compiler can be recompiled and all tests can be run using:

  • $ ./scripts/test-self.sh

Status

Ralph is not actively maintained.

If you have questions, are interested in using it, or even would like to continue its development, just open a new issue!