=head1 NQP - Not Quite Perl (6)

NQP is Copyright (C) 2009 by Patrick R. Michaud.  See F<LICENSE>
for licensing details.

This is "Not Quite Perl" -- a compiler for quickly generating PIR
routines from Perl6-like code.  The key feature of NQP is that it's
designed to be a very small compiler (as compared with, say, perl6
or Rakudo) and is focused on being a high-level way to create
transformers for Parrot (especially hll compilers).  In addition,
unlike Rakudo, NQP attempts to restrict itself to generating code
that can run in Parrot without the existence of any NQP-specific
runtime libraries.

=head2 Building from source

NQP comes bundled with Parrot, so if you have a recent Parrot
distribution you likely also have a copy of NQP.  Inside of a
Parrot installation NQP is known as C<parrot-nqp>.

To build NQP from source, you'll just need a C<make> utility
and Perl 5.8 or newer.  To automatically obtain and build Parrot
you may also need a Git client.

To obtain NQP directly from its repository:

    $ git clone git://github.com/perl6/nqp-rx.git

If you don't have git installed, you can get a tarball or zip
of NQP from github by visiting http://github.com/perl6/nqp-rx/tree/master
and clicking "Download".  Then unpack the tarball or zip.

Once you have a copy of NQP, build it as follows:

    $ cd nqp-rx
    $ perl Configure.pl --gen-parrot
    $ make

This will create a "nqp" or "nqp.exe" executable in the
current (nqp-rx) directory.  Programs can then be run from
the build directory using a command like:

    $ ./nqp hello.pl

The C<--gen-parrot> option above tells Configure.pl to automatically
download and build the most appropriate version of Parrot into a
local "parrot/" subdirectory, install that Parrot into the
"parrot_install/" subdirectory, and use that for building NQP.
It's okay to use the C<--gen-parrot> option on later invocations
of Configure.pl; the configure system will re-build Parrot only
if a newer version is needed for whatever version of Rakudo you're
working with.

You can use C<--parrot-config=/path/to/parrot_config> instead
of C<--gen-parrot> to use an already installed Parrot for building
NQP.  This installed Parrot must include its development
environment; typically this is done via Parrot's C<make install>
target or by installing prebuilt C<parrot-devel> and/or C<libparrot-dev>
packages.  The version of the already installed Parrot must satisfy a
minimum specified by the NQP being built -- Configure.pl will
verify this for you.  Released versions of NQP always build
against the latest release of Parrot; checkouts of the HEAD revision
from github often require a version of Parrot that is newer than
the most recent Parrot monthly release.

Once built, NQP's C<make install> target will install NQP
and its libraries into the Parrot installation that was used to
create it.  Until this step is performed, the "nqp" executable
created by C<make> above can only be reliably run from the root of
NQP's build directory.  After C<make install> is performed
the executable can be run from any directory (as long as the
Parrot installation that was used to create it remains intact).

If the NQP compiler is invoked without an explicit script to
run, it enters a small interactive mode that allows statements
to be executed from the command line.  Each line entered is treated
as a separate compilation unit, however (which means that subroutines
are preserved after they are defined, but variables are not).

=head2 Differences from previous version of NQP

* Sub declarations are now lexical ("my") by default, use
  "our sub xyz() { ... }" if you want package-scoped subroutines.

* The  PIR q<...>;  construct is gone.  Use Q:PIR or pir::opcode(...)
  instead.

* The mainline code of modules is no longer tagged as ":load :init"
  by default.  Use  INIT { ... }  for any code that you want to be
  run automatically at startup.

* Cuddled else's are no longer valid Perl 6, 'else' requires a
  space after it.

* Double-quoted strings now interpolate $-variables.