Boomerang is a programming language for writing lenses—well-behaved bidirectional transformations —that operate on ad-hoc, textual data formats.

Boomerang grew out of the Harmony generic data synchronizer, which grew out of the Unison file synchronization project.

• Aaron Bohannon, J. Nathan Foster, Benjamin C. Pierce, Alexandre Pilkiewicz, and Alan Schmitt. Boomerang: Resourceful Lenses for String Data. In ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages (POPL), San Francisco, California, January 2008. full text
• J. Nathan Foster, Alexandre Pilkiewicz, and Benjamin C. Pierce. Quotient Lenses. To appear in ACM SIGPLAN International Conference on Functional Programming (ICFP), Victoria, British Columbia, September, 2008. full text alternately host