$ show haskell/fgl
The Functional Graph Library (FGL) is a Haskell library providing an inductive approach to graph data structures and algorithms. It offers multiple graph implementations (Tree-based and PatriciaTree-based) with varying performance characteristics, along with a comprehensive suite of graph algorithms including BFS, DFS, shortest path, max flow, min span tree, articulation points, biconnected components, dominators, and transitive closure. The library features a modular architecture with clear separation between core graph type classes, basic operations, and specific query algorithms. It supports both pure functional and monadic (imperative-style) graph manipulation, with utilities for automatic node labeling and graph construction. The library is actively maintained with recent updates supporting modern GHC versions and includes a thorough test suite with QuickCheck properties.
The LLM identified 3 files worth highlighting for reuse:
Self-contained pairing heap implementation with O(1) insert and merge operations. Demonstrates advanced functional data structure techniques with lazy evaluation and amortized complexity guarantees. Could be used as a standalone priority queue in other projects.
Utility for automatic node label to integer ID mapping with stateful generation. Provides bidirectional lookup and automatic ID allocation. Demonstrates skilled use of State monad for managing mappings in pure functional context. Extractable as a general-purpose labeling utility.
Collection of threading combinators for managing state through computations. Includes threadList, threadMaybe, and parallel split operations. Shows advanced functional programming patterns for state manipulation that could be applied in various contexts beyond graph processing.