[Pyparsing] Stuck on recursive parsing

[Gre7g L. <haf...@ya...>]

Hey guys, I'm brand new to pyparsing and I'm already
stuck.

My boss wants me to make our product "scriptable", so
I'm trying to write some Python code to compile an
expression entered by the user into something the
hardware can execute. Basic op-codes such as +, -, *,
and / were easy enough to compile with
operatorPrecedence, but I got in trouble when I tried
to make my code handle pre-defined function calls.

I wrote this using Forward and <<, but pyparsing isn't
going for it. Here's a minimal fragment of code
illustrating what I was trying to do:

http://pastie.textmate.org/162526

As you can see, it's trying to compile the expression
"2-5*abs(-6)+3". I was hoping it would return
something like:

[[2, '-', [5, '*', ['abs' + '(' + ['-' + 6] + ')']]
    '+' 3]]

but instead I got:

[[2, '-', [5, '*', 'abs']]]

It looks kind of like operatorPrecedence interpretted
'abs' as a literal and then got confused when it hit
the parenthesis, and gave up.

Can anyone suggest a way to work around this?

Many thanks and my apologies if this has been
discussed at length. If so, I'd love a link to a
pertinent post.

Gre7g

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