#4148: improve new recursive do syntax
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Reporter: guest | Owner:
Type: feature request | Status: new
Priority: low | Milestone: 7.6.1
Component: Compiler | Version: 6.12.3
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by lerkok):
Hi Simon,
[Looks like Iavor and I (Levent) got confused for each other again; I
should've explicitly put my name under that long message, my apologies.]
I completely agree with the solution you've outlined:
* Bring "mdo" notation back, which does all the analysis. (As it was
implemented in GHC the first time.)
* Keep "rec", which is a simple wrapper with mfix; no analysis.
* Both features turned on with just one flag, @RecursiveDo@ being the
obvious choice.
There's one hiccup though: What happens if someone uses a "rec" block
inside an "mdo"? I think it would be best if such uses were grammatically
flagged as syntax errors: "rec" should only be available inside an
immediately enclosing "do". Does that make sense?
Thanks,
-Levent.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4148#comment:13>
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