Add abs and sign functions for vec types and fix neg operator

[kmarchais]

Description

This pull request proposes the following changes that I personally needed:

• Implementation of the abs and sign functions for vec types
• Fix for a bug with the neg operator

Changes Made

• vec.h → Added abs and sign functions for vec types
• builtins.py → Added built-in abs and sign functions for vec types
• types.py → Corrected the neg operator, which was expecting an extra y parameter.

Testing

I didn't change any test because I don't understand the following issues

• For the abs and sign functions, tests will probably be similar to those for min and max. However, min and max tests are not run due to slow compile time.
• While the test for the neg operator appeared to pass, an error was encountered when the operator was used.

[c0d1f1ed]

Thanks for this proposal and the accompanying code changes!

We're going to need a different license and have contributors sign an agreement, before we can merge public MRs. We're working towards that but it might take a while.

Also, the proposed functionality in this MR all sounds very useful, but we have to balance it against the run-time compilation impact of larger headers. I'm currently working on changes that should give us more headroom for that (using pre-compiled headers), and we'll put benchmarks in place to ensure the tradeoffs are well balanced.

Thanks for your patience. Note that in the meantime you could use @func to write your own helper functions that implement this functionality, instead of making them part of the wp.* builtins.

[christophercrouzet]

Hi @kmarchais, this is just to let you know that the abs() and sign() built-ins for vectors have been merged into the main branch, and the issue with the neg operator was fixed a while ago already. Thanks for your pull request!