Chaddaï Fouché [EMAIL PROTECTED] writes:
so you need an f so that c `f` x is c (for any c and x) and
yet (b `f` c) is c for any c and b -- this is impossible (or
I'm asleep).
Well, it isn't impossible but quite hard (and not even standard H98
if I'm not mistaken)
If it is possible, I'm
16 Aug 2007 10:11:24 +0100, Jon Fairbairn [EMAIL PROTECTED]:
snip my quote
I certainly wouldn't count such a thing as a valid
solution. It's always amazed me that C uses as standard a
mechanism of ending strings that is so obviously an
error-prone hack.
I'm completely with you on that !
Kurt Hutchinson wrote:
On 8/15/07, Alexteslin [EMAIL PROTECTED] wrote:
I am really sorry, but i still can't define the function. The chapter the
exercise is in precedes algebraic types or Maybe a types. And is seems that
must being easy to define.
I answered some exercises on using foldr such
2007/8/15, Aaron Denney [EMAIL PROTECTED]:
The original last fail on empty list, it's far easier to obtain the
same semantic with foldl than with foldr, in fact it isn't hard at all
to make it polymorphic without hassle (contrary to the foldr case)
_if_ you remember that there _is_ a
On 2007-08-15, Chaddaï Fouché [EMAIL PROTECTED] wrote:
Still I don't see why foldl would make it harder to use Maybe than
foldr (in fact it's easier).
You're right. I just wasn't looking at it quite properly.
--
Aaron Denney
--
___
Haskell-Cafe
Alexteslin [EMAIL PROTECTED] writes:
I am really sorry, but i still can't define the function. The chapter the
exercise is in precedes algebraic types or Maybe a types. And is seems that
must being easy to define.
I answered some exercises on using foldr such as summing for example, but
On 2007-08-14, Alexteslin [EMAIL PROTECTED] wrote:
Hi,
I am trying to do the exercise which asks to define built-in functions
'last' and 'init' using 'foldr' function, such as last Greggery Peccary =
'y'
the type for my function is:
myLast :: [Char] - Char
I am not generalizing type
(Quoting reformatted. Try to have your responses below what you are
responding to. It makes it easier to read as a conversation.)
On 2007-08-14, Alexteslin [EMAIL PROTECTED] wrote:
Aaron Denney wrote:
Folds replace the cons operator (:) with the function you pass it.
If you want the tail of
On 2007-08-14, Chaddaï Fouché [EMAIL PROTECTED] wrote:
2007/8/14, Alexteslin [EMAIL PROTECTED]:
Well, i have tried cons (:) operator but when it passed to foldr doesn't work
because cons operator operates first character and then the list but the
foldr argument takes a function (a-a-a). Maybe
2007/8/14, Aaron Denney [EMAIL PROTECTED]:
The problem with foldl is that you can't easily make it polymorphic
because of how the null case is handled. foldl1 and foldr1 are trivial,
true.
The original last fail on empty list, it's far easier to obtain the
same semantic with foldl than with
On 2007-08-14, Chaddaï Fouché [EMAIL PROTECTED] wrote:
2007/8/14, Aaron Denney [EMAIL PROTECTED]:
The problem with foldl is that you can't easily make it polymorphic
because of how the null case is handled. foldl1 and foldr1 are trivial,
true.
The original last fail on empty list, it's far
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