add strict map functions for Array and SmallArray #138
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| let go i | i == sizeofArray a | ||
| = return () | ||
| | otherwise | ||
| = do x <- indexArrayM a i |
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It might be worth mentioning in a comment that we use indexArrayM here in case f is lazy.
| #if HAVE_SMALL_ARRAY | ||
| mapSmallArray' f sa = createSmallArray (length sa) (die "mapSmallArray'" "impossible") $ \smb -> | ||
| fix ? 0 $ \go i -> | ||
| when (i < length sa) $ do |
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Why < here and == for Array?
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I'm not really sure. I just copied the implementation of fmap for SmallArray to get this. I think the better question is why does everything in SmallArray use fix while everything in Array uses explicit recursion?
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History, I imagine. The fix seems to avoid the need for a local type signature in the go function. I have no idea how the generated code compares, but that would be worth checking.
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I'm inclined to leave this as is for now. I'd like to open a separate PR adding benchmarks that check the difference between these two styles.
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I cut down and reworded the comment. There are two reasons to want to perform the lookup eagerly, and this is not the place to explain that. Aside from holding references to the array, we don't want to build a thunk to perform the lookup. |
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Your wording is certainly more concise. Thanks! |
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