[Haskell-beginners] Haskell type system

[Peter Verswyvelen]

well, depending on what you do and don't understand, the explanation can
very from short to very long, so it might help to try to explain what you
don't understand for each question/answer. usually when you try to explain
what you don't understand, you will understand it, so that's always a good
way to start :)
On Sun, Sep 27, 2009 at 3:32 PM, informationen <informationen at gmx.de> wrote:

> 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 <informationen at gmx.de>
>> 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.)
>>
>>
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>
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