Your wish is my IO (). If I break, you can: 1. Restart: M-x haskell-process-restart 2. Configure logging: C-h v haskell-process-log (useful for debugging) 3. General config: M-x customize-mode 4. Hide these tips: C-h v haskell-process-show-debug-tips Changed directory: /home/trifon/fmisync/Courses/2019_20/FP_2019_20/sandbox/lectures/haskell/ λ> (:) 1 [] [1] λ> (:) 1 ((:) 2 []) [1,2] λ> tail ((:) 1 ((:) 2 [])) [2] λ> (\1 -> 5) 2 *** Exception: :12:2-8: Non-exhaustive patterns in lambda λ> (\1 -> 5) 1 5 λ> (3 > 1) && (f 2 == 10) *** Exception: /home/trifon/fmisync/Courses/2019_20/FP_2019_20/sandbox/lectures/haskell/Lazy.hs:3:1-7: Non-exhaustive patterns in function f λ> (3 < 1) && (f 2 == 10) False λ> take 5 [1..100000000000000000000000000000] [1,2,3,4,5] λ> head (1:[2..1000000000000]) 1 λ>