#15646: ghci takes super long time to find the type of large fractional number -------------------------------------+------------------------------------- Reporter: Johannkokos | Owner: | JulianLeviston Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: GHCi | Version: 8.4.3 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by JulianLeviston):
C. Change the representation of Ratio to have an extra constructor that represents numbers of the form N / D * 10**E.
It feels to me that this (C) is the best of the 3 options, probably because it's the '''laziest'''. Ideally we don't want to compute anything until the last possible moment, I'd reckon. As far as I can tell from section 2.5 of the report, the type of '''any''' literal where there's an `e` marking the exponent is going to be `Fractional a => a`. Can we not short circuit on this, and then keep the value as Ratio (ie "c" above) until its actual value is needed? I'm a bit curious that computing `time ./inplace/bin/ghc-stage2 -e '1e10000000 :: Float'` takes a long time to render `Infinity` but I guess this issue would go away when we fix the typechecking bug. I don't think choosing '''B''' is really an option because that'd involve changing the Haskell report. As I'm pretty new, some direction would be good. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15646#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler