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Bug when trying to combine two lists

    • Closed Issue created by sutbult @trac-sutbult

    I want to write a function that takes two lists and returns a list that includes every possible combination of elements from the two given lists, using a given function. I thought that this code would work:

    combine :: (a -> b -> c) [a] -> [b] -> [c]
combine fn alist blist = [fn a b | a <- alist, b <- blist]

    However, when compiling, this message arises from GHC:

    Glasgow Haskell Compiler, Version 8.2.1, stage 2 booted by GHC version 7.10.3
Using binary package database: /Library/Frameworks/GHC.framework/Versions/8.2.1-x86_64/usr/lib/ghc-8.2.1/package.conf.d/package.cache
Using binary package database: /Users/samuelutbult/.ghc/x86_64-darwin-8.2.1/package.conf.d/package.cache
package flags []
loading package database /Library/Frameworks/GHC.framework/Versions/8.2.1-x86_64/usr/lib/ghc-8.2.1/package.conf.d
loading package database /Users/samuelutbult/.ghc/x86_64-darwin-8.2.1/package.conf.d
wired-in package ghc-prim mapped to ghc-prim-0.5.1.0
wired-in package integer-gmp mapped to integer-gmp-1.0.1.0
wired-in package base mapped to base-4.10.0.0
wired-in package rts mapped to rts
wired-in package template-haskell mapped to template-haskell-2.12.0.0
wired-in package ghc mapped to ghc-8.2.1
wired-in package dph-seq not found.
wired-in package dph-par not found.
package flags []
loading package database /Library/Frameworks/GHC.framework/Versions/8.2.1-x86_64/usr/lib/ghc-8.2.1/package.conf.d
loading package database /Users/samuelutbult/.ghc/x86_64-darwin-8.2.1/package.conf.d
wired-in package ghc-prim mapped to ghc-prim-0.5.1.0
wired-in package integer-gmp mapped to integer-gmp-1.0.1.0
wired-in package base mapped to base-4.10.0.0
wired-in package rts mapped to rts-1.0
wired-in package template-haskell mapped to template-haskell-2.12.0.0
wired-in package ghc mapped to ghc-8.2.1
wired-in package dph-seq not found.
wired-in package dph-par not found.
*** Chasing dependencies:
Chasing modules from: *Combine.hs
!!! Chasing dependencies: finished in 0.69 milliseconds, allocated 0.222 megabytes
Stable obj: []
Stable BCO: []
Ready for upsweep
  [NONREC
      ModSummary {
         ms_hs_date = 2018-12-23 17:18:05.830132761 UTC
         ms_mod = Main,
         ms_textual_imps = [(Nothing, Prelude)]
         ms_srcimps = []
      }]
*** Deleting temp files:
Deleting: 
compile: input file Combine.hs
*** Checking old interface for Main (use -ddump-hi-diffs for more details):
[1 of 1] Compiling Main             ( Combine.hs, Combine.o )
*** Parser [Main]:
!!! Parser [Main]: finished in 1.05 milliseconds, allocated 0.171 megabytes
*** Renamer/typechecker [Main]:
*** Deleting temp files:
Deleting: 
*** Deleting temp dirs:
Deleting: 
ghc: panic! (the 'impossible' happened)
  (GHC version 8.2.1 for x86_64-apple-darwin):
	repSplitAppTys
  a_anL[sk:1]
  b_anM[sk:1] -> c_anN[sk:1]
  []
  Call stack:
      CallStack (from HasCallStack):
        prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable
        callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable
        pprPanic, called at compiler/types/Type.hs:808:9 in ghc:Type

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
    Edited by Ben Gamari
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