[Haskell-cafe] Call for discussion: OverloadedLists extension
simonpj at microsoft.com
Mon Sep 24 19:19:07 CEST 2012
| I remember a similar discussion a few years ago. The question of whether
| or not overloading list literals a good idea notwithstanding, the problem
| with this is that fromList for vectors is highly inefficient. So if
| something like this gets implemented and if vector/array literals are one
| of the main motivations then I really hope there will be no lists
Would you like to remind us why it is so inefficient? Can't the vector construction be a fold over the list? Ah... you need to know the *length* of the list, don't you? So that you can allocate a suitably-sized vector. Which of course we do for literal lists.
So what if fromList went
fromList :: Int -> [b] -> a b
where the Int is the length of the list?
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