Address some of the fusion issues in #202 #241
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it is marked as `NOINLINE` and has no rules that match on it otherwise, so no fusion can happen.
it would previously replace `takeWhileEnd p` with
S.reverse . S.takeWhile p . S.reverseStream
But `S.reverse` can only fuse with its argument, and `S.reverseStream`
only fuses with its consumer. So all possible fusion is within this
pipeline, and in the best case we obtain a direct implementation.
There might be some value in this if we had a
`S.reverseStream/S.reverse` rule, so that in multiple chained invocations
of `takeWhileEnd` we could eliminate some intermediat steps. But no such
rule exists at the moment.
There is a comment that > length needs to be phased after the `compareN/length` rules otherwise > it may inline before the rules have an opportunity to fire. but these rules are marked `[~1]`, so we can inline `length` in phase 1 to expose the `stream` in its definition and actually allow it to fuse.
This mirrors commits 1e10823, just for strict functions.
as it does a case match.
because `dropWhileEnd` is not.
it was matching on `singleton`, but `singleton` gets rewritten to `s.singleton`. An additional rule makes this robust.
because the rules for `dropWhile` are only enabled before phase 1
nomeata
added a commit
to nomeata/inspection-testing
that referenced
this pull request
Nov 17, 2018
which I have submitted in haskell/text#241
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Is this mergeable? |
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@nomeata yes, it's mergeable... thanks :-) |
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in most cases, just updating the docs. More interesting stuff for
takeWhileEndandlength, see the corresponding commits. See #202.