Re: [GHC] #12665: Make Read instances for Integral types faster, and make them fail fast

#12665: Make Read instances for Integral types faster, and make them fail fast -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: feature request | Status: new Priority: high | Milestone: 8.2.1 Component: Core Libraries | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"bef7e784d037f720697a215b9e21f13b385e6d3e/ghc" bef7e78/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="bef7e784d037f720697a215b9e21f13b385e6d3e" Read parentheses better Instead of pulling a token and looking for `'('` or `')'`, just look for the character itself. This prevents us from lexing every single item twice, once to see if it's a left parenthesis and once to actually parse it. Partially fixes #12665 Make parens faster more aggressively * Strip spaces before parsing, so we never have to strip the same spaces twice. * String parsers together manually, to try to avoid unnecessary closure creation. Test Plan: Validate Reviewers: austin, hvr, bgamari Reviewed By: bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D2630 GHC Trac Issues: #12665 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12665#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler