Breakpoint 0 activated at Test6.hs:5:8-11
Stopped in Main.main, Test6.hs:5:8-11
_result :: a = _
*** Exception: Prelude.head: empty list
CallStack (from HasCallStack):
  error, called at libraries/base/GHC/List.hs:1590:3 in base:GHC.List
  errorEmptyList, called at libraries/base/GHC/List.hs:74:11 in base:GHC.List
  badHead, called at libraries/base/GHC/List.hs:70:28 in base:GHC.List
  head, called at Test6.hs:1:8 in main:Main