Move

Move is a simple but powerful programming language which can run on most computers (anywhere there’s a >=ES3 JavaScript runtime). When compared to JavaScript, Move has the following key features:

• Simpler. E.g. there’s only one way to declare functions, no need for var declarations, only a single type of equality operators and no need for terminating statements with semicolons.

• Less boiler-plate code needed. Move introduces a few carefully selected features like the “import” and “export” keywords, and @-shorthand for this access.

• Move runs in any >=ES3 JavaScript runtime and thus can be used as a universal programming language for everything from running in web browsers to powering complex offline systems.

A simple Move program which prints “Hello John” three times:

hello = ^(name){ "Hello "+name }
repeat {times: 3} ^{
  print hello {name: "John"}
}

Same program as above, but using shorthand call-style:

hello = ^(name){ "Hello "+name }
repeat 3, ^{ print hello "John" }

Move compiles directly to optimized JavaScript which can run on almost any computer (in a web browser or a runtime like Node.js).

The above program compiles down to the following JavaScript:

"use strict";
var repeat = Move.runtime.repeat,
    print  = Move.runtime.print,
    hello  = function hello(name) {
  // <keyword argument logic here>
  return "Hello " + name;
};
return repeat(3, function () {
  return print(hello("John"));
});

Note: The above JavaScript has been simplified for the purpose of demonstration.

Installing and using Move

For now, it’s easiest to install Move using the Node Package Manager:

sudo npm install -g move

Then require the “move” module before requiring any move code. In this example.js we load “foo.mv” which is a module written in Move:

require("move");
var foo = require("./foo");

There’s also a simple API which can be accessed from the move module:

var move = require("move");
console.log(move.compile("bar = ^{ 5 * Math.PI }"));
// Output:
//   var bar;
//   bar = function bar() {
//     return 5 * Math.PI;
//   };

If you want to use move in a web browser, simply use and include the move.js file (no dependencies). Including this file will export a single global symbol called “move” (window.mv) which contains the Move library (see lib/index.js) including functionality for compiling and executing Move code as well as providing the ES5 normalizing but small runtime library. Have a look at web/try/index.html for inspiration.

Extras

There are some extras (or “support stuff”) which can be found in the extras directory. For instance, a TextMate bundle adding Move syntax support including commands like Cmd+R to run a Move program, Cmd+B to compile and display generated JavaScript, Cmd+Shift+B to compile and display the AST. Some of these commands require Node.js to be installed.

Differences to JavaScript

• Functions are declared using one single expression: ^(arg1){...} and can be called using either keyword arguments or positional arguments. Functions without arguments can be written as ^{... or ^(){... (parenthesis are optional).

  • In JavaScript, there are two different ways to define a function: using the function expression and the function declaration statement, the latter having subtle restrictions. Move only has function expressions and all but strictly anonymous functions are named, providing a richer stack trace when debugging.

  • As functions, or lambdas, are the key awesomeness of JavaScript and is a very light-weight thing, the “function” keyword and boilerplate argument parens just need to be easier to write. Move uses the ^ keyword and does not enforce () for argument-less functions.

  • The last statement in a function is automatically returned.

  • Functions can be called using the foo {key: value} syntax, passing arguments by name. This greatly increases code readability.

  • Functions can be called using the foo value, ... syntax, passing arguments in a simple succession. This feature allows Move to have a very limited set of language keywords and instead implement things like print, repeat, create, etc as regular functions. For instance, this allows for creating DSL-like extensions to the language.

  • When defining functions, any argument can be given a default value using either : or =. E.g. foo = ^(bar, baz: 4, names=[], age) {....

• Variables are implicitly declared – Move will automatically declare (i.e. “create and attach”) a newfound variable in the scope which it first was used. The use of “var” produces a syntax error. A variable will only be declared if there’s no variable with the same name which is reachable from the current scope (this is possible since the Move compiler is AST-aware).

• No commas required to terminate expressions. Move will determine when a comma is needed so you don’t have to (and the code gets more readable).

• No type-coercing equality operators – in Move, == does not perform type coercion and behaves just like === in JavaScript. Same goes for !=.

• @-shorthand for accessing properties of the this object. E.g. this.foo = 5 can be written as @foo = 5.

• Importing CommonJS modules can be done using the import statement. E.g. rather than the tedious var module1 = require("module1") boilerplate, you can write import module1

• Exporting CommonJS modules is aided by the export statement. E.g. instead of writing var foo = exports.foo = function () {... you can write export foo = ^{... (or even export foo if foo is defined elsewhere).

• A small runtime library makes Move ES5 normalized even in non-ES5 environments. This means less feature probing and less boiler-plate code. Things like Array.isArray, Object.create and String.prototype.trim are all guaranteed to be available and function according to the ES5 standard.

Move is designed for humans which is the reason for why things like variable declarations and statement terminators has been removed – they are simply not part of the essentials or essence of what a programmer should be thinking about. The computer is, or at least should be, better at deciding those things.

Most features mentioned above can be toggled in the Move compiler. For instance, compiling code with the raw option set to true will generate free-standing/self-hosted JavaScript. It’s also possible to toggle language features, like setting the keywordArguments to false which disabled the use of keyword arguments. See lib/index.js (the “compile” function) for a complete list of options.

License (MIT)

Move incorporates some third-party source, namely a derivation of UglifyJS. These sources have a separate license embedded into their heads.

The rest of Move is licensed as follows:

Copyright © 2011 Rasmus Andersson http://rsms.me/

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.