On Mon, May 23, 2011 at 4:29 PM, Johan Tibell wrote:

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Because unboxing can not be used for the polymorphic value component in

On Mon, May 23, 2011 at 4:18 PM, Sebastian Fischer wrote: the

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strict structure and there is no way to tell GHC to unbox the specific instantiation `IntMap (Lazy a)`?

Exactly. This would amount to code generation in the module defining IntMap (Lazy a), similar to how C++ implements template.

I see. Given that library authors currently work around the lack of this optimization it's probably a Good Thing to add it to GHC. But that is a separate topic as it seems impractical to extend GHC before containers gets updated. Sebastian