On 2/8/08, Matthew Naylor
it in for an efficient program. However, to my knowledge, it is an unwritten rule of Haskell compilers that sharing *is* preserved, and that they do perform *graph* reduction. Clean, a similar language to
I'm not sure that programmers ought to be relying on this rule. Sure, all Haskell compilers I know of preserve sharing and do graph reduction. But conventional wisdom is not the same thing as an unwritten rule. Someday, someone might come along and write a Haskell compiler that isn't based on graph reduction and doesn't preserve sharing at the implementation level (while still preserving the informal semantics of Haskell). A programmer who had written code that failed to compile correctly under this hypothetical compiler would be a very naughty Haskell programmer indeed.
Haskell, indeed has a semantics based on graphs. So I don't believe
Haskell doesn't have a semantics, graph-based or not... or at least not a formal one, and if not a formal one, I don't know what you mean :-) Cheers, Tim -- Tim Chevalier * http://cs.pdx.edu/~tjc * Often in error, never in doubt "There are no sexist decisions to be made. There are antisexist decisions to be made. And they require tremendous energy and self-scrutiny, as well as moral stamina..." -- Samuel R. Delany