Janis Voigtländer. Semantics and Pragmatics of New Shortcut Fusion Rules. In Jacques Garrigue, Manuel V. Hermenegildo, editors, Functional and Logic Programming, 9th International Symposium, FLOPS 2008, Ise, Japan, April 14-16, 2008. Proceedings. Volume 4989 of Lecture Notes in Computer Science, pages 163-179, Springer, 2008. [doi]
We study various shortcut fusion rules for languages like Haskell. Following a careful semantic account of a recently proposed rule for circular program transformation, we propose a new rule that trades circularity for higher-orderedness, and thus attains better semantic properties. This also leads us to revisit the original foldr/build-rule, as well as its dual, and to develop variants that do not suffer from detrimental impacts of Haskell’s mixed strict/nonstrict semantics. Throughout, we offer pragmatic insights about our new rules to investigate also their relative effectiveness, rather than just their semantic correctness.