Subj : Walking through script syntactic tree
To   : netscape.public.mozilla.jseng
From : BegemoT
Date : Thu May 26 2005 10:46 pm

Hello, All!
    I use Rhino embedded engine in my application. In host enviroment I have
some set of  objects, each of them identified by uniq string ID. User can
write
some kind of script to evaluate an expression depends on some of this
object's
properties.
    Thing that I want to do is to, given a script code, find what objects
are using in it.
Where are two reasons for what -- one, as users supposed to have only basic
programming experience, I want to allow them refer my object by simply use
their
ID as variable name, e.g then user write script like distance(Object1,
Object2), I want
to find, that "Object1"  and "Object2" is IDs of some objects in host
enviroment and
create appropriate variables (Object1,Object2) in current score, given them
values
of appropriate objects, before executing script. Second reason is perfomance
issue -- 
knowing on which objects expression value is depends allow to recalculate it
only then
required.
    So, as far as I can understand, I should use Rhino Parser directly, to
parse
user's script and make some processing of resulting syntactic tree. I see,
from Rhino
sources, what parsed arbitrary script I got ScriptOrFunctionNode as root.
So, my
question is: how I can walk through each node in this tree? I feel myself
rather confusing
with first-next-last notation used in this tree structure....
    Another question is how I can find undeclared variables nodes in this
tree? Now, I can
find only one way to do somthing like this -- searching for nodes with type
== Token.NAME,
but it is not exactly the thing -- in expression distance(Object1, Object2)
I see NAME nodes
[distance, Object1, Object2] -- how I can determine, what "distance" is a
function name, not
variable? Is it possible in JS syntax at all? -- functions in JS is
variables, only with special
content, as far as I know, but it seems obvious, what with given full
sintactic tree it is possible
to distinct function call operation on an object from property access/rvalue
using, it is not obvious
only HOW to do so :) Any ideas?

Thanks in advance!
Ruslan.

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