#4278: Proposal: Add strict versions of foldlWithKey and insertLookupWithKey to
Data.Map
---------------------------------+------------------------------------------
Reporter: tibbe | Owner:
Type: proposal | Status: new
Priority: normal | Component: libraries (other)
Version: 6.12.3 | Keywords:
Testcase: | Blockedby: 4277
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Runtime performance bug
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This proposal depends on #4277.
The current Data.Map API lacks two important functions:
* A strict left (pre-order) fold -- needed to e.g. sum all the values in
a map efficiently.
* A strict `insertLookupWithKey'` -- needed to e.g. update an integer
counter and retrieve the previous value in a single traversal.
The benchmark we ran indicates that `foldlWithKey'` is 95% faster than its
lazy counter part. `insertLookupWithKey'` is only 6% faster, but the
speedup is highly dependent on how many times each element is update. Each
element was only updated once in our benchmark so real speedups should be
larger.
The consideration period is 3 weeks.
Note that the attached patch includes the dependent patches in the above
linked ticket.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4278>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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