#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 simonpj): Would you like to lay out the design, and its moving parts, in a draft Note that will eventually be part of the source code? eg I think (but am not sure) that your question is this: in representation of a literal fractional number: {{{ data FractionalLit = FL { fl_text :: SourceText -- How the value was written in the source , fl_neg :: Bool -- See Note [Negative zero] , fl_mantissa, fl_exp :: Integer -- Denotes <mantissa>E<exp> } }}} in what number base is the `fl_exp` expressed? For example * `1.7e30` has `fl_mantissa = 17`, and `fl_exp = 29`, assuming base 10 * But what about `0x5e.ff2p12`? Here the mantissa can reasonably still be `0x5eff`, but the exponent must (presumably, given [http://downloads.haskell.org/~ghc/master/users-guide/glasgow_exts.html #hexadecimal-floating-point-literals the spec]) be in base 2. To me it sounds as if we need another field for the exponent base to accurately represent the literal. So the value of the literal is `mantissa * (base ^ exponent)`. My instinct is just to make the a sum-type rather than another `Int` or `Integer`: {{{ data ExponentBase = Base10 | Base 2 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15646#comment:33 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler