Changes between Version 17 and Version 18 of FoldrBuildNotes


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Timestamp:
Sep 1, 2014 2:55:15 PM (5 years ago)
Author:
dfeuer
Comment:

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  • FoldrBuildNotes

    v17 v18  
    6161A: See #9398. This seems almost to work out, but then it doesn't quite—things that are unboxed when the current implementation is used aren't, and it can be very bad.
    6262
    63 Q: Why isn't `scanr` a good producer?
    64 
    65 It's actually possible to rewrite `scanr` using `build` and `foldr`, but there's a wrinkle: the way it's currently written, `scanr` can ''inspect'' the list as it creates it. This becomes impossible once `build` is in play. To work around that, you can hang on to a second copy of the head of the list. But then you need somewhere to *put* that. Whoops, that's allocation.
    66 
    6763Q: Why does making one thing fuse sometimes make something else not fuse?
    6864