Re: [Haskell] Re: [Haskell-cafe] ANN: cmonad 0.1.1

Duncan and I have thought about this too, exactly as you describe. (Just !x) => (# tag#, x# #) -- Don lennart:

When I looked at it a year ago or so, it was a return of one constructor in a sum. Looking at core, you can see several places where a function is called and that function always returns the same constructor, so the case analysis of the return value is not needed; it should be returned as an unboxed tuple instead I'll see if I can get a simple example to illustrate the problem.

I talked to Simon PJ about it and he thought an analysis and transformation for such a thing would be a good idea, but someone has to do the work, of course.

Another unrelated problem, I think, is that ghc needs to promote in-memory variables to registers when possible. Perhaps the new code generator has such a transformation?

-- Lennart

On Mon, Mar 30, 2009 at 3:28 AM, Don Stewart wrote:

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Nested constructed product returns? Or constructed sums?

lennart:

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Well, yes and no.  GHC actually does a decent job when given very imperative code with references and mutable arrays. Now the type I use to wrap the references to get type safe l-values and r-values makes it tricker, and ghc lacks a crucial optimization for specialization of constructor returns. With that in place I think the code could be quite performant.