On Mon, Sep 24, 2012 at 5:53 AM, George Giorgidze <giorgi...@gmail.com>wrote:
> Our second approach to OverloadedLists is to avoid the construction of > lists altogether. By typechecking and desugaring lists like > > [] ; [x,y,z] ; ['a' .. 'z'] ; > > as > > mempty ; singleton x `mappend` singleton y `mappend` singleton z ; > genericEnumFromTo 'a' 'z' ; > This is very interesting. As Michael mentions later, we already have mechanisms in place to work around the creation of constant strings for the Text and ByteString types, and they rely on a combination of GHC rewrite rules and knowledge about the internal representation of constant strings used by GHC. We are fortunate that GHC uses a very efficient representation to store constant strings, so doing the translation is efficient. Constant lists are another story entirely (for good reason); the generated object files are bloated and poorly laid out, when for simple types (integers and whatnot), I'd really like to see a packed array in the .data section. I would be interested to see if an approach that avoids list construction can also aim to achieve a more efficient object file layout, with the implied goal being to make fast translation to the runtime representation easily achievable.
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