README.pyv8

Combining PyJS and PyV8 to produce an Optimising Python Compiler
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pyjs.py is a stand-alone python-to-javascript.  PyV8 provides python
bindings to the V8 Javascript Execution library, which provides fast
JIT-compiled x86 and ARM assembler of a javascript application.

Combining the two back-to-back would logically provide a way to
compile python scripts to x86 or ARM assembler, resulting in a competitor
to Psyco with the added advantage of supporting ARM CPUs.

pyv8run.py demonstrates how this can be achieved.  It takes as input
as its first argument a filename to be compiled to javascript and
handed to the PyV8 execution engine.  More advanced versions of this
principle would involve the creation of cached precompiled versions
of scripts and modules, both the javascript (.pyj) and the JIT
assembler (.py8).

Dependencies
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You will require both the v8 library and pyv8.  They can be obtained
from these locations:

    http://code.google.com/p/v8
    http://code.google.com/p/pyv8

Follow the build instructions for each - you will not, at this time,
be able to work on x86_64 platforms: you _will_ need to install 32-bit
versions of python and boost-python (and development headers).
As v8 is compiler technology, porting v8 to 64-bit is a major
undertaking that has not yet been attempted.

Testing
-------

very simple!

echo print "hello" > test.py
./pyv8run.py ./test.py

What's Going On?
----------------

pyv8run.py uses pyjs.py and simply adds PyV8 as yet another "platform".
Presently, the only function override that's supported is pyjslib.printFunc,
which can be found in pyjamas/library/platform/pyjslibPyV8.py and this
simple example is sufficient to demonstrate the principle.

In the PyV8-platform-specific version of printFunc, a global routine
named "print_fn" is called.  A class named Global which has a function
named "print_fn" is then passed in to the PyV8 execution engine.
The pyjs compiler knows that when a "print" statement is encountered,
it must output "pyjslib_printFunc([print's arguments]);".  In this
roundabout fashion, we eventually arrive back at "print", back inside
pyv8run's Global.print_fn().

In an ideal world, the PyV8 library would not be needed: a simple
command-line tool similar to smjs (from spidermonkey) would suffice.
However, the power of PyV8 comes from being able to access real
python c-based dynamic modules, as sloisel's early experimental
project (also named pyv8) showed.  In that work, which also used
python-boost, sloisel managed to import Tcl/Tk into a pyv8 application,
and had javascript firing up a python Tcl/Tk window, thanks to being
able to gain access to the methods of the standard python c-based tk
dynamic module.