How do I modify a variable in Haskell?

Re:How do I modify a variable in Haskell? by tome on Tuesday August 15, 2017 @11:47AM (#15019294)

FWIW. (Haskell doesn't have a convenient built-in function for printing arrays. Guilty as charged!)

    size = 10
    
    main = do
      -- Initialise the array to 0
      arr <- newArray ((1,1), (size, size)) 0
      let _ = arr :: IOArray (Int, Int) Int

      -- Set the diagonal to 1    
      forM_ [1..size] $ \i -> writeArray arr (i,i) 1
    
      -- Print the array
      forM_ [1..size] $ \i -> do
        forM_ [1..size] $ \j -> do
          a <- readArray arr (i, j)
          putChar (if a == 0 then '0' else '1')
          when (j == size) (putChar '\n')

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Re:How do I modify a variable in Haskell? by Ajedi32 on Tuesday August 15, 2017 @12:02PM (#15019419)

Thanks, that looks much nicer and more in-line with what I'd expect from an example intended to demonstrate how easy a simple task is in a specific language.

As an aside, Ruby doesn't have a built-in function for printing arrays either (unless you count .inspect or .to_s, which let you print _anything_). The code I gave formatted the array as a string using some simple data manipulation functions before printing it; it was intended to match the output of the program you provided.

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