mapnik/mapnik — pull request #1234 by lightmare (2012-05-30 15:43:55+00:00)
Title: unary minus operator on mapnik::value and in expression_grammar

We needed to rotate text in the opposite direction, but orientation="-[angle]" wouldn't parse (and "select -angle as angle" from db is ugly). Although "0-[angle]" or "-1*[angle]" actually work, I though it'd be nicer to have a proper unary minus operator in expressions.

A funny feature this patch introduces is -[text] : the operation had to be defined somehow, so I made it return the text reversed ;)
```
-[text]
```