#15646: ghci takes super long time to find the type of large fractional number -------------------------------------+------------------------------------- Reporter: Johannkokos | Owner: (none) 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):
But this relies on laziness, no?
No, it doesn't rely on laziness. At no stage will GHC construct that Rational. The desugarer will generate something like {{{ Var 'fromRational' `App` (Var 'readRational' `App` Lit (LitString "1e100")) }}} That is, it'll generate Core that will, when compiled and run, compute the rational (at runtime). But the compiler just manipulates this Core data structure, there is no bad Rational in it. Does that help? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15646#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler