Stream fusion in Haskell is done with rewrite rules. On the one hand, it's totally true that you're no longer really writing Haskell, and the facility for rewr

Stream fusion in Haskell is done with rewrite rules. On the one hand, it's totally true that you're no longer really writing Haskell, and the facility for rewrite rules itself needed (at some point) to be added to the compiler. But at this point I can make my own data structures fuse (potentially in new ways) without further changes to the compiler. https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html#rewrite-rules https://downloads.haskell.org/~ghc/latest/docs/html/users_gu...