Compositional breadth-first walks.
An experimental control structure for defining breadth-first walks in trees and graphs in a compositional manner.
Weave is an applicative transformer for multi-level computations. This library actually defines multiple variants of Weave with different performance profiles. The most useful ones are Weave.Lazy and Weave.Oblivious. Two other variants Weave.Strict and Weave.Endless are included mainly as curiosities.
The main application of Weave is to define breadth-first monadic unfolds. Examples of such unfolds for some general-purpose tree structures can be found under the namespace Weave.Unfold, for each variant of Weave.
See also my blog post: Unfolding trees breadth-first in Haskell.
Internally, to avoid duplication, those unfolds are implemented as a Backpack mixin Weave.Unfold. This package might not work with Stack, which doesn't support Backpack. For minimal dependencies and no backpack, the weave-core library is also available, containing only the Weave types.