An indicator function is a function , where is a set. Indicator functions can be thought to represent the subset of given by the preimage of 1. An indicator is any callable object in C++, which takes in a single argument, and returns a boolean. Indicators are used in Pastel to filter out candidates, for example in nearest neighbors searching, where it is often desirable to ignore the searched point itself.
Accepts all objects.
Accepts objects rejected by another indicator.
Rejects all objects.
Rejects a given point but accepts otherwise.
Accepts based on comparison to a reference object.