#16089: seq is not cooperating with :sprint in GHCi as expected -------------------------------------+------------------------------------- Reporter: radrow | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 8.6.3 Resolution: | Keywords: seq sprint | strictness Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: #7253, #16096 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by osa1): My fix for #16096 (Phab:D5473) fixes the original reproducer: {{{ ~ $ ghc-stage2 --interactive GHCi, version 8.7.20181227: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/omer/rcbackup/.ghci λ:1> x = [True, False] λ:2> :sprint x x = [True,False] λ:3> :print x x = [True,False] }}} Here's a slightly more complex example: {{{ ~ $ ghc-stage2 --interactive GHCi, version 8.7.20181227: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/omer/rcbackup/.ghci λ:1> x = [ 1.. ] :: [Integer] λ:2> :sprint x x = _ λ:3> x `seq` () () λ:4> :sprint x x = 1 : _ }}} However if I omit the type annotation in the first line it doesn't work as expected: {{{ ~ $ ghc-stage2 --interactive GHCi, version 8.7.20181227: https://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/omer/rcbackup/.ghci λ:1> x = [ 1.. ] λ:2> x `seq` () () λ:3> :sprint x x = _ }}} I'd expect to see the same output `x = 1 : _` here. We should use this one as the reproducer. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16089#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler