#4148: improve new recursive do syntax
---------------------------------+------------------------------------------
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: |
---------------------------------+------------------------------------------
Changes (by simonpj):
* cc: ryani (added)
* difficulty: => Unknown
Comment:
I believe that both Iavor and Ross advocate:
* Revive the `mdo` keyword (enabled by `RecursiveDo`)
* Make `mdo` perform dependency analysis / segmentation
* Keep the `rec` keyword (enabled by `DoRec`)
* Cease doing dependency analysis / segmentation for `rec`
So `mdo` is clever and does the segmenting stuff, but `rec` says "do
exactly what I say" which gives precise control if you need it.
To me that seems simple, predictable, and makes everyone happy. I suppose
that if we ''stop'' doing segmentation for `rec` some programs might
change behaviour, but I bet they are very few. (Opinions, Ross, Iavor?)
It seems a bit overkill to have two language flags for what is really one
feature. An alternative would be to make them synonymous for now, and
deprecate `DoRec` in favour of `RecursiveDo`.
Opinions? As Iavor says this is not a big deal. But presumably Ryan had a
reason for raising it.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4148#comment:12>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
