#13377: Compiler error: Simplifier ticks exhausted -------------------------------------+------------------------------------- Reporter: | Owner: (none) simplifierticks | Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Windows Architecture: x86_64 | Type of failure: Compile-time (amd64) | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- 2.4 Programming jointly with types and values Exercise 2.4.1 (Fixpoint). The lambda term: y = = \f->(\x->f (x x)) (\x->f (x x)) (that encodes a fixed point combinator in the untyped lambda calculus) does not type check in Haskell. Try it! Interestingly though, recursion on the type level can be used to introduce recursion on the value level. If we define the recursive type: data F a = = F { unF :: F a->a } then we can “annotate” the definition of y with applications of F and unF such that y typechecks. Do it! This works on someones else his computer: {{{#!hs data F a = F { unF :: F a -> a } -- y = \f -> (\x -> f (x x)) (\x -> f (x x)) y = \f -> (\x -> x $ F x) (\x -> f . unF x $ x) }}} Compiler error: ghc.EXE: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-mingw32): Simplifier ticks exhausted When trying UnfoldingDone x_s1Gq To increase the limit, use -fsimpl-tick-factor=N (default 100) If you need to do this, let GHC HQ know, and what factor you needed To see detailed counts use -ddump-simpl-stats Total ticks: 6480 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Increased -fsimpl-tick-factor to 100.000 still the error occurred -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13377 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler