[Haskell-cafe] How to print a string (lazily)

Daniel Carrera daniel.carrera at zmsl.com
Tue Jan 3 12:32:20 EST 2006


I've been studying more Haskell and I've improved a lot. But I just hit 
a small problem. I want to print all the elements of a linst (putStr). 
I'd like to write something like this:

print_list [] = do putStr ""
print_list (x:xs) = (do putStr x) && print_list xs

I know this is wrong, but I hope you can see what I'm trying to do.

I know of other ways I could print a list. For example:

print_list xs = do putStr(join xs)
	where join [] = ""
	      join (x:xs) = (show x) ++ "\n" ++ join xs

But the thing is, I want to write a lazy version of this function. It's 
not that I need such a function, I'm just trying to learn Haskell.

Any suggestions?

Question: What do you call a function that has side-effects? (like 
putStr) I know that "function" is the wrong term.

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