Re: [Haskell-beginners] Haskell type system

For the parts you could answer and only the correct answers. But every hint would be of great value. I searched the web and the haskell wiki, especially http://www.haskell.org/haskellwiki/Category:Theoretical_foundations, for further informations, but found none, so if you could point me to a good tutorial for that kind of question, that would be of help too.

Which parts would like explanations for? All of them?

On Sun, Sep 27, 2009 at 12:22 PM, informationen wrote:

Hi,

i am trying to understand the Haskell type system. I thought i understood it quite well until i encountered the three following exercises. As you can see, i have the answers already. But i don't understand, why they are correct.

Could anybody tell me a good place where i could learn how to answers these kind of questions correctly or could give me some explanations, why these answers are correct?

Any help is highly appreciated.

Kind regards

Chris Two functions f and g with the following signatures are given: f :: a -> a g :: b -> c -> b

A) Give the type of the following expressions:

1) g [False] True  :: 2) g [] True       :: 3) g (f True)      :: 4) g f             :: Answers:

1 [Boolean] 2) [a]          3) c -> Bool 4) c -> (a -> a)1)  g f 1       B) Which of the following statements is correct?

2)  g (f 1)         is type correct 3)  g . (f 1)       is type correct 4)  g . f 1         is type correct 5)  (g . f) 1       is type correct 6)                  none of the expressions is correct

Answers: 1,2 and 5 are correct.

C) A function h is given as: h p x = p (f x). Which of the following statements is correct.

1) h :: a -> b -> a -> b 2) h :: (a -> a) -> a -> a 3) h :: (a -> b) -> a -> b 4) h is equivalent to h' with h' p = p . f 5) h is equivalent to h' with h' p = p f 5) h is equivalent to h' with h' p x = p f x

Answers: (I am not sure, if i remember correctly, but 3) and 4) should be correct.)

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners