#1473: isSpace is too slow -------------------------------------+------------------------------------- Reporter: igloo | Owner: Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: | Version: 6.6.1 libraries/base | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by dfeuer): * cc: hvr, ekmett (added) Comment: I wrote up a whole long comment here, but then TRAC timed me out and I lost it. The gist of it is that I don't think we should be using `iswspace` here at all, because Haskell 2010's [https://www.haskell.org/onlinereport/haskell2010/haskellch16.html specification of `isSpace`] appears to be intended to match [http://www.unicode.org/Public/6.3.0/ucd/PropList.txt the Unicode concept of whitespace], which does not seem to match the locale-specific [http://pubs.opengroup.org/onlinepubs/009695399/functions/iswspace.html definition of `iswspace`]. As I discussed with Carter, we can probably improve the performance of `isSpace` by using something like Yitzchak Gale's implementation modified to cut down the number of branches (since many of them will be mispredicted). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/1473#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler