RE: [Haskell-cafe] Are newtypes optimised and how much?

| >> Yes, you can freely use Foo/unFoo. There's no runtime penalty. (In the | >> jargon of GHC's intermediate language, Foo and unFoo translate to | >> *type-safe casts*, which generate no executable code. | > | > When does the conversion to type-safe casts occur relative to other | > optimizations (namely, rewrite rules)? | | That is, I know that rewrite rules operate on the source language not on | Core, but to what extent does that mean that type-safe casts inhibit the | firing of rules? Rewrite rules work on Core, not source, so they "see" the type-safe casts. I don't know how to say "to what extent" they inhibit rules. If you show an example I will try to help. S