BUILDING PUGS
-------------

Pugs needs the Glasgow Haskell Compiler (GHC), preferably version 6.6 or above.
At the moment the minimum requirement is GHC 6.4.1 or above, but we plan to
discontinue support for GHC 6.4.* in the next release.

To install GHC, download a binary build from http://haskell.org/ghc/.
Although source code for GHC is available, it will take a very long time to
build by yourself.

Additionally, Pugs uses the Cabal framework (http://haskell.org/cabal/),
which is usually bundled with GHC itself.

v6-pugs (see <http://perlmonks.org/?node_id=559083>) needs the CPAN modules
Devel::Caller, Module::Compile and Pugs::Compiler::Rule. The first one is
dependent on Module::Build with C_support, so install ExtUtils::CBuilder and
ExtUtils::ParseXS first. Satisfy all with one command:

    $ sudo cpan -fi ExtUtils::CBuilder ExtUtils::ParseXS Module::Build \
          Devel::Caller Module::Compile Pugs::Compiler::Rule

http://jnthn.net/perl6/ has binary builds for Win32.  For Mac OS X (PowerPC),
http://www.unobe.com/packages/ has binary builds too. If you'd like to build
Pugs by hand, http://wiki.kn.vutbr.cz/mj/?Perl%206%20and%20Parrot has some
instructions.

For dynamic loading/inlining of Haskell modules, you should install the
hs-plugin library, available here:

    http://www.cse.unsw.edu.au/~dons/code/hs-plugins

To install Pugs on your system, simply type this in the command line:

    cpansign -v         # optional; see SIGNATURE for details
    perl Makefile.PL
    make                # or 'nmake' on Win32
    make test
    make install

Both make and make test can take a long time (perhaps hours).

To change the installation location, pass PREFIX=/opt/wherever to 
Makefile.PL like so:

    perl Makefile.PL PREFIX=/your/prefix/here

XXX NOTE!!!!!!!!
PREFIX doesn't actually work right now. So ignore what I just said. But if
it did work, that's how you would do it.

Do not set PREFIX to your Perl 5 installation dir, as that would overwrite
some of the files there with their Pugs counterparts.

ENVIRONMENT VARIABLES
---------------------

There are several environment variables that control pugs's build process.

You may use the GHC environment variable to set the ghc executable before 
you run "perl Makefile.PL", for example:

    export GHC=${HOME}/bin/ghc (bash)
    setenv GHC ${HOME}/bin/ghc (csh)
    
To control which optional subsystems are embedded in Pugs, set the 
PUGS_EMBED variable. For example: 
 
    export PUGS_EMBED="parrot noperl5" (bash)
    setenv PUGS_EMBED "parrot noperl5" (csh)

Perl5 is now embedded by default.  Use "noperl5" to disable.

To build with an embedded parrot interpreter, make sure the PUGS_EMBED 
variable contains "parrot", and set the PARROT_PATH variable to point to 
the directory in which you checked out the parrot source tree. For example:
 
    export PARROT_PATH=${HOME}/src/parrot (bash)
    setenv PARROT_PATH ${HOME}/src/parrot (csh)

MAKE TARGETS
------------

The default make target builds an optimized Pugs. This means that Pugs will
be slower to compile, but will run much faster. To disable this, run:
    
    make fast

To run the test suite with a pretty HTML matrix showing test results:

    make smoke

To turn on profiling in the GHC compiler:
 
    make prof

To hack on Pugs using the GHC interactive shell:

    make ghci

BUILD CONFIGURATION CONSOLIDATION VIA config.yml
------------------------------------------------

To keep the multitude of configuration options and mechanisms under
control for the build, we're moving over some of the above to a
centralized file, "config.yml" under the build root. This file is in
YAML format[1]; if it does not exist, one with defaults will be created
for you.

The options you can control there include:

- optimization level: whether `make` means `make optimized` or
  `make unoptimized` by default.

- precompilation options: by default, pugs is built with the Standard Prelude
  compiled into it. This makes many Perl 6 builtins available to pugs, and
  loads fast. You can specify additional modules to inline a precompiled
  version of into the executable: Test.pm is a good choice if running the
  test suite. The cost of this is a longer build process which requires much
  more RAM.

- GHC heap size: if precompiling modules other than Prelude.pm into pugs, you
  will probably need to increase the amount of RAM GHC permits itself to use,
  otherwise it will abort the build. And if your machine is low on RAM, and
  itself runs out of memory while building pugs, you can set this to a low
  value (but turn off optimization and precompilation too).

- install_dir: if set, `make install` will put everything under this
  directory. Do not set this to your Perl 5 installation, since that
  will overwrite some of the files there with the Pugs counterparts
  (as will make install PREFIX= as noted above.)

You can override values set in this file temporarily via the single
PUGS_BUILD_OPTS environment variable. For example, if you normally do
precompile Prelude.pm but want a faster build just this once:

    env PUGS_BUILD_OPTS=precompile_prelude=false make

See `util/config-template.yml` for more information.

[1] See <http://yaml.org/>. Only a subset of the YAML syntax is permitted
at the moment, to avoid a dependency on the full parser.