#2646: Expand folding options for Sets and Maps
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Reporter: sedillard | Owner:
Type: proposal | Status: new
Priority: normal | Component: libraries (other)
Version: 6.8.3 | Severity: normal
Keywords: containers | Testcase:
Architecture: Unknown/Multiple | Os: Unknown/Multiple
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xref #2580 ,
http://www.haskell.org/pipermail/libraries/2008-September/010653.html ,
http://www.haskell.org/pipermail/libraries/2008-October/010782.html
I've attached a patch which expands on Evan's changes and propagates them
to `IntSet` and `IntMap`.
Some (possibly controversial) changes of note :
* Added foldr and foldl functions for the map types. This is
redundant, but so is much of the interface. The argument to foldlWithKey
has a strange type, (a -> key -> value -> a), that does not play nicely
with flip and const. So I think its convenient to have foldl as well, and
since we've got that why not throw foldr in too.
* Specialized default implementations of foldl and foldr for Foldable
class. This is perhaps better than exporting then from the map libraries.
Data.Sequence does it this way, but the map libraries do not. If the API
clutter is found to be unbearable then perhaps a major cleanup is in
order, hiding all folds in the map/set modules and exporting them via
Foldable.
Shall I also add strict versions?
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2646>
GHC <http://www.haskell.org/ghc/>
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