This section defines boolean properties of Unicode characters. This means, a character either has the given property or does not have it. In other words, the property can be viewed as a subset of the set of Unicode characters.
The GNU libunistring library provides two kinds of API for working with
properties. The object oriented API uses a type
to designate a property. In the function-based API, which is a bit more
low level, a property is merely a function.