README.rst

How to install

git clone https://github.com/arclanguage/arc-nu.git

You also need Racket.

If you're on *nix you can probably get it with your distribution's package manager, like apt-get or yum or whatever.

If you're on Windows or Mac OS X, get Racket here.

How to run

If you're on Windows, double click on the arc.bat file.

If you're on *nix or Mac OS X, use path/to/arc-nu/arc

---

If you don't want to type out the path to arc every time, you can place a symlink in your $PATH

Doing so is a bit involved, and depends on what distribution you're using. On Debian/Ubuntu-based systems, this should work:

mkdir -p ~/bin
ln -s path/to/arc-nu/arc ~/bin/arc

Now logout or reboot your computer. If it went well, you should be able to use arc rather than path/to/arc-nu/arc

---

You can use arc foo to load the Arc file foo.arc

And the arc executable is suitable for writing shell scripts:

#! /usr/bin/env arc
(prn "foo")

Use arc -h to see all the available options.

Why?

So, why would you want to use it over Arc 3.1 or Anarki?

• It's faster! Arc/Nu strives to be at least as fast as Arc 3.1, and in some cases is significantly faster. For instance, (+ 1 2) was 75.21% faster in Arc/Nu than in Arc 3.1, last time I checked.

• In addition to supporting Arc 3.1, the Arc/Nu compiler can also support other languages. All languages supported by Arc/Nu can communicate with each other and use libraries defined in other languages.

• Includes an import macro which makes it significantly easier to load files:

  ; Arc 3.1
  (load "/path/to/foo.arc")
  
  ; Arc/Nu
  (import foo)
  

• The REPL is implemented substantially better:

  • Ctrl+D exits the REPL

  • Ctrl+C aborts the current computation but doesn't exit the REPL:

    > ((afn () (self)))
    ^Cuser break
    >
    

  • Readline support is built-in, which means:

    • Pressing Tab will autocomplete the names of global variables:

      > f
      filechars    find         flat         for          fromdisk
      file-exists  findsubseq   flushout     force-close  fromstring
      fill-table   firstn       fn           forlen
      

    • Pressing Up will recall the entire expression rather than only the last line:

      > (+ 1
           2
           3)
      6
      > (+ 1
           2
           3)
      

• You can use the arc executable to write shell scripts:

  #! /usr/bin/env arc
  (prn "foo")
  

  This is like arc.sh in Anarki but implemented in Racket rather than as a bash script, so it should be cleaner and more portable.

  In addition, it supports common Unix idioms such as:

  $ arc < foo.arc
  $ echo "(+ 1 2)"       | arc
  $ echo "(prn (+ 1 2))" | arc
  

  This idea is courtesy of this thread

• Like Anarki, Arc/Nu provides a form that lets you bypass the compiler and drop directly into Racket. In Anarki this form is $ and in Arc/Nu it's %:

  > (% (let loop ((a 3))
         (if (= a 0)
             #f
             (begin (displayln a)
                    (loop (- a 1))))))
  3
  2
  1
  #f
  

  This also lets you call Arc/Nu and Racket functions that aren't exposed to Arc:

  > (%.->name +)
  +
  
  > (%.string? "foo")
  #t
  

• [a b c] is expanded into (square-brackets (a b c)) which is then implemented as a macro:

  (mac square-brackets (body)
    `(fn (_) ,body))
  

  Likewise, {a b c} is expanded into (curly-brackets (a b c))

  This makes it easy to change the meaning of [...] and {...} from within Arc

• The Arc/Nu compiler is written in Racket, rather than mzscheme

• Arc/Nu cleans up a lot of stuff in Arc 3.1 and fixes bugs (Anarki also fixes some bugs in Arc 3.1, but it generally doesn't clean things up)

• Arc/Nu has reorganized Arc 3.1 significantly, hopefully this makes it easier to understand and hack

• All special forms (assign, fn, if, quasiquote, and quote) are implemented as ordinary Arc macros

• For more details on the differences between Arc/Nu and Arc 3.1, see this page