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[p5sagit/p5-mst-13.2.git] / jpl / README

Copyright 1998, O'Reilly & Associates, Inc.

This package may be copied under the same terms as Perl itself.

Disclaimers
-----------
This is a work in progress, and relies on bleeding-edge technology
from the network.  Don't expect not to be surprised occasionally.

Requirements
------------
Perl 5.005_02 (or later) must be compiled and installed as a shared library
(libperl.so).  I had to use the system's malloc.  JPL was originally built
and tested with 5.004_04 and early Java 1.1 development kits.  This version
has not been well tested under 5.005_02, so you can expect some rough edges.

You need JDK 1.1.  On Solaris 1.1.5 has been verified to work.  Linux
users can try the latest version (1.1.3 or later) available from (for
example):

  ftp://ftp.blackdown.org/pub/Linux/JDK/1.1.3/updates/libjava-1.1.3v2-1.tar.gz

The get_jdk directory contains a script that will download JDK (but not
the patch file above) off of the net for you.  (This presumes you've
already installed the modules mentioned in ../README.)

You may need to ensure that all files under the ../jpl directory are writable.
install-jpl expects to be run with super-user privileges so that it can
put things in the right places.

What the heck is JPL?
---------------------
JPL is a hybrid (to use the polite term) language.  It's basically Java
in which the methods can optionally be implemented by Perl code.  A
preprocessor called "JPL::Compile" looks at your .jpl file and spits
out the appropriate .java, .c, .h, .pl, and .so files to accomplish the
desired task.  Hopefully a lot of those files can go away in the future
as jpl mutates into a Perl-to-Java compiler.  The long-term goal is for
jpl to be able to take a pure Perl file and spit out a java .class
file.  This initial version of JPL is an attempt to begin to mesh the
semantics of Java and Perl.  Some people may find it useful in its
current form, but you should know right up front that we've still got a
ways to go with it.  A journey of a thousand miles continues with the
second step...

JPL Syntax
----------
JPL syntax is trivial, given that you know Java and Perl.  Pretend like
you're writing a native Java method, but say "perl" instead of
"native", and then instead of omitting the body of the method, put your
Perl code in double curlies.  (See Sample.jpl for an example.)

Calling back from Perl to Java is done through the JNI (Java Native
Interface).  No weird transmogrifications are done by the preprocessor
to your Perl code--it's all normal Perl.  The preprocessor just wraps
it up into funny subroutines you don't see unless you peek at the .pl
file it generates.

Installation
------------
Run "install-jpl".  You have to tell it whether you want to use the
current directory for JPL_HOME or some other directory.  Everything
else should take care of itself, except that after install-jpl
writes the setvars program, you are responsible to invoke it properly
before any JPL applications can be compiled under the current shell.

    sh:   eval `setvars -sh`
    csh:  eval `setvars -csh`
    perl: eval `setvars -perl`;

More Info
---------

You can look at the Sample and Test directories, as well as the ../eg
directory for examples.

Perhaps the most important bit of advice we can give you is to watch

    http://perl.oreilly.com

for further information on how to get further information.

Have the appropriate amount of fun.