Re: [Haskell-beginners] Error message: "Couldn't match expected type"

Oh... my... Thank you so much. Maybe, I'm confused with C. Fix main() to main, it works! =) Thank you again, and have a nice day. Sincerely, Sok 2014-10-03 1:49 GMT+09:00 Brandon Allbery :

On Thu, Oct 2, 2014 at 12:40 PM, S. H. Aegis wrote:

...

main() =

You have declared (well, described, but by type inference that's the same thing) main to take a parameter of type "unit" (empty tuple). main doesn't take parameters.

Haskell parameters do not work the way most common languages do; using parentheses in function calls the way you would in C/Java/Python etc. will generally get you unexpected type errors, because you're telling it you're passing tuples around. So, the function call

f() (f :: () -> a)

is different from

f (f :: a)

and the function call

f(a, b) (f :: (a,b) -> c)

is different from

f a b (f :: a -> b -> c)

(The inferred type of `f` is shown after each call.)

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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