You're right on #1 - for other nodes you could also look at how the parser
creates them (or ask if there's something particularly tricky).
For #2 there isn't a good way to do this right now. You could cheat and do it
with private reflection for the time being. First you need to create a
PythonAst object (no problem, it's public). That will hold onto the tree you
created and lets you control some knobs on how the code gen will proceed. You
just need to call PythonNameBinder.BindAst(ast, compilerContext) (which is
internal so reflection use #1) and then ast.TransformToAst (also internal,
reflection use #2) which will return you a DLR LambdaExpression. From there
you could go to the DLR and ask them to compile the lambda
(Expression<T>.Compile) or you could produce a ScriptCode object for it which
you can run. The way we produce a ScriptCode once we have the lambda is:
if ((pythonOptions.Module & ModuleOptions.Optimized) != 0) {
return new OptimizedScriptCode(lambda, sourceUnit);
} else {
// TODO: fix generated DLR ASTs
lambda = new GlobalLookupRewriter().RewriteLambda(lambda);
return new ScriptCode(lambda, sourceUnit);
}
And you can basically do the same thing. The 1st path will leak memory if
you're doing it repeatedly so you probably want the re-write & normal
ScriptCode.
We could probably do a little refactoring to expose this functionality onto
PythonAst so that you can just new one of those up and get a ScriptCode back
but it seems too much like a feature for it to make 2.0 at this point.
On #3 unfortunately I didn't get our CodeDom code generator into 2.0 in time so
it'll wait for the next release - mainly because I didn't have a chance to port
the v1.0 tests forward. But it's pretty easy to grab it from the v1.1 sources
and update it as our AST hasn't changed very much.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dan Eloff
Sent: Wednesday, October 08, 2008 1:42 PM
To: Discussion of IronPython
Subject: [IronPython] Using IronPython AST
I'm looking at the ast stuff in IronPython.Compiler.Ast and seeing how
difficult it would be to write a python 2.5 _ast (and 2.6 ast) wrapper
over it.
Jython actually supports this now, and I don't wish to see IronPython
left behind in this area.
It looks like I should be able to handle a read-only ast without much
difficulty. The trouble comes with altering the ast. It seems from
looking at the code that everything is marked readonly, the ast cannot
be modified in place?
This is not a blocker, it's possible to handle all modifications in
the wrapper, and then generate a new ast at the end that can be
evaluated.
For example:
node = UnaryOp()
node.op = USub()
node.operand = Num()
node.operand.n = 5
1) How would you turn this into an ast? Something like this maybe?
node = new UnaryExpression(PythonOperator.Negate, new ConstantExpression(5))
2) I assume there is a mechanism for compiling and/or executing an
ast, please could someone show how to use it (you can build off the
script below)
3) Is there a mechanism for turning an ast back into source code? This
would help me with debugging.
Thanks,
-Dan
Thanks to Dino for showing how to get an ast:
import clr
clr.AddReference('IronPython')
clr.AddReference('Microsoft.Scripting')
clr.AddReference('Microsoft.Scripting.Core')
from IronPython.Compiler import Parser
from Microsoft.Scripting import ErrorSink
from Microsoft.Scripting.Runtime import CompilerContext
from Microsoft.Scripting.Hosting.Providers import HostingHelpers
from IronPython.Hosting import Python
py = Python.CreateEngine() # beta 5 and beyond
src = HostingHelpers.GetSourceUnit(py.CreateScriptSourceFromString('print
"hello"'))
pylc = HostingHelpers.GetLanguageContext(py)
p = Parser.CreateParser(CompilerContext(src,
pylc.GetCompilerOptions(), ErrorSink.Default), pylc.Options)
ast = p.ParseFile(True)
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