Proposal: Value strict versions of containers

Sebastian Fischer fischer at
Tue May 24 09:37:59 CEST 2011

On Mon, May 23, 2011 at 4:29 PM, Johan Tibell <johan.tibell at>wrote:

> On Mon, May 23, 2011 at 4:18 PM, Sebastian Fischer <fischer at>
> wrote:
> > Because unboxing can not be used for the polymorphic value component in
> the
> > 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

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