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  1. Practice
  2. Functional Programming
  3. Introduction
  4. Hello World N Times
  5. Discussions

Hello World N Times

  • alsuga + 4 comments

    Lang: Haskell
    I'm learning haskell, if someone have a suggestion or a correction please let me know

    hello_worlds 1 = putStrLn "Hello World"
hello_worlds n = do
        putStrLn "Hello World" 
        hello_worlds (n - 1)

main = do
   n <- readLn :: IO Int
   hello_worlds n
    • FengkieJ + 1 comment

      doing loop by recursion! cool man, you done it right. there's more elegant way to solve it, but your solution shows how a fp supposed to be written.

      • kaushala + 1 comment

        Any way to loop other than this? Thanks in advance

        • sfelde21 + 0 comments

          @kaushala nope

    • zefciu + 1 comment

      Maybe more elegant and DRY:

      hello_worlds 0 = return ()
      • ftreale + 0 comments

        Not only more elegant, but this code considers the test value 0, which should be tested IMHO.

    • sfelde21 + 1 comment

      what does this line do?

      hello_worlds 1 = putStrLn "Hello World"
      • aleksei_maide + 1 comment

        I wasn't sure either (new to haskell), but apparently it's a stop condition. (If the input to the function is 1 then it simply does the following: putStrLn "Hello World")

        • 0xb0b1 + 1 comment

          I think it's not the way you said "stop condition", it's a pattern matching for specifying which value the function should return for the given value, in this case: 1 But you're right about saying it simply does the following for 1. :)

          • ftreale + 0 comments

            Yes, hello_worlds 1 = putStrLn "Hello World" is pattern matching. When the hello_words function is called with input 1, that is the executed line. However, in Haskell, the base of recursions are often expressed with a pattern match, so I think is fair to also say it's a stop condition.

    • Hertzz + 1 comment

      I've had many issues with this mostly bc of the function getManyLines that editor provides and I've ended up cutting it down to basicly your hello_worlds. It prints hello world ten times, and the editor is still saying the outpust is wrong. Also, shouldn't haskell functions be defined for all possible inputs? Does anybody have good sources for learning Haskell? turns out to be much more difficult then object oriented Langs

      • alsuga + 0 comments

        http://learnyouahaskell.com/