Re: [Haskell-cafe] commenting out a line of code

The answer is very simple ;-} The report says that after a do the first symbol to encounter determines the indentation level; so putStrLn “done” is part of the else branch. Obvious, isn’t it. Se also https://wiki.haskell.org/Common_Misunderstandings Doaitse

Op 15 nov. 2016, om 13:31 heeft Norbert Melzer het volgende geschreven:

I'm not quite sure, but I'd guess either one of

1.) It does not compile at all because of suspicious indentation 2.) It will just print "A" but not "done" because that is considered beeing in the else-branch.

Johannes Waldmann mailto:johannes.waldmann@htwk-leipzig.de> schrieb am Di., 15. Nov. 2016 um 13:11 Uhr: Dear Cafe -

Sometimes, a comment can change the meaning of a program. No? Well, but "commenting out" a line of code certainly does. So, can you guess what this program will output?

main = do if True then do putStrLn "A" else do -- putStrLn "B" putStrLn "done"

I nominate this for inclusion in a hypothetical Haskell equivalent of http://www.javapuzzlers.com/ http://www.javapuzzlers.com/

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