Control.Selective.Rigid.Free

This is a library for selective applicative functors, or just selective functors for short, an abstraction between applicative functors and monads, introduced in this paper: https://dl.acm.org/doi/10.1145/3341694.

This module defines free rigid selective functors. Rigid selective functors are those that satisfy the property <*> = apS.

Intuitively, a selective functor f is "rigid" if any expression f a is equivalent to a list of effects chained with select operators (the normal form given by the free construction). In contrast, "non-rigid" selective functors can have non-linear, tree-like shapes, because * nodes can't be straightened using the <*> = apS equation.