How to install

::

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

You also need Racket <http://racket-lang.org/>_.

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 <http://racket-lang.org/download/>_.

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 <http://arclanguage.org/item?id=10344>_

• 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 <doc/Differences.rst>_