Expand folding options for Sets and Maps
xref #2580 (closed) , 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?
Trac metadata
| Trac field | Value |
|---|---|
| Version | 6.8.3 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | libraries (other) |
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