Hi Neal,

Thank for you the quick response & suggestion. That is the obvious workaround I 
missed. :)

As for the contributing docs, I’ll put something together and submit a PR.

Thank you again!

Best,
Troy

> On Jul 24, 2020, at 15:23, Neal Richardson <[email protected]> 
> wrote:
> 
> 
> I can't answer the first question authoritatively, though off the top of my 
> head, could you translate that to `0 - x` and use the binary operator? You 
> may also consider posting this question to the [email protected] mailing 
> list.
> 
> As for contributing tutorials and user guides, yes, please do. I believe the 
> right location to add what you're talking about would be in 
> https://github.com/apache/arrow/tree/master/docs/source/python.
> 
> Neal
> 
>> On Fri, Jul 24, 2020 at 12:42 PM Troy Zimmerman <[email protected]> wrote:
>> Hi,
>> 
>> I’ve written a small library that uses the ast module to parse a Python 
>> expression into a Gandiva expression tree. I’d like to able to do numeric 
>> negation (i.e. -x) in an expression, but I’ve I looked through the source 
>> code and haven’t found a way to achieve this. (I could also be missing an 
>> obvious workaround.)
>> 
>> Separately, are there any tutorials on using the Python bindings for 
>> Gandiva? If not, would the project be open to such a contribution? At the 
>> moment I’ve got scattershot notes of what I’ve learned from digging through 
>> the source, but could organize them into a brief tutorial or cookbook.
>> 
>> Best,
>> Troy

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