#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: | -------------------------------------+------------------------------------- Changes (by osa1): * keywords: type => newcomer Comment: It seems like adding one more digit in the literal causes 10x increase in desugaring + type checking time: {{{ ~ $ echo ':t 1e10000000' | time ghci ... ghci 0,37s user 0,04s system 97% cpu 0,418 total ~ $ echo ':t 1e100000000' | time ghci ... ghci 3,63s user 0,12s system 99% cpu 3,749 total ~ $ echo ':t 1e1000000000' | time ghci ... ghci 43,77s user 1,68s system 100% cpu 45,429 total }}} I also tried compiling this {{{#!haskell a = 1e1000000000 }}} and it also takes forever. I suspect this is a type checker bug or a desugarer bug. I think this would be a good newcomer ticket. I'd start with finding how the expression `1e1000000000` parsed, and then find relevant desugarer and type checker code. Then add some print statements around those code to which one takes so long. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15646#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler