Can you do dropWhile in terms of foldr?
One can write foldr that represents drop or dropWhile of the
original foldr. One can do even more: zip two folds. That is,
obtain a fold that is equivalent to zipping up two lists represented
by the original folds. Even furthermore, one can do all these
Can you do dropWhile in terms of foldr? I don't see how.
If you are really keen, you might want to try altering the working
backwards with tuples version into one which is properly lazy (many
people who read the paper pointed out the omission).
you might want to mention the story of the
I'm sure this has been done a hundred times before, but a simple generalization of foldl just
occurred to me and I wonder if there's anything like it in the standard libraries (I couldn't find
anything). Basically, I was trying to define the any function in terms of a fold, and my first
try
On Wed, Jul 04, 2007 at 04:20:20PM -0700, Michael Vanier wrote:
I'm sure this has been done a hundred times before, but a simple
generalization of foldl just occurred to me and I wonder if there's
anything like it in the standard libraries (I couldn't find anything).
Basically, I was trying
That's cool -- good point. takeWhile is also trivially defined in terms of
foldr:
takeWhile p = foldr (\x r - if p x then x:r else []) []
Can you do dropWhile in terms of foldr? I don't see how.
Mike
Stefan O'Rear wrote:
On Wed, Jul 04, 2007 at 04:20:20PM -0700, Michael Vanier wrote:
I'm
On Wed, Jul 04, 2007 at 05:08:01PM -0700, Michael Vanier wrote:
That's cool -- good point. takeWhile is also trivially defined in terms of
foldr:
takeWhile p = foldr (\x r - if p x then x:r else []) []
Can you do dropWhile in terms of foldr? I don't see how.
dropWhile cannot be
On Thursday 05 July 2007 11:20, Michael Vanier wrote:
Again, I'm sure this has been done before (and no doubt better); I'd
appreciate any pointers to previous work along these lines.
Takusen is, if I recall correctly, based around a generalised fold supporting
accumulation and early
2007/7/4, Michael Vanier [EMAIL PROTECTED]:
That's cool -- good point. takeWhile is also trivially defined in terms of
foldr:
takeWhile p = foldr (\x r - if p x then x:r else []) []
Can you do dropWhile in terms of foldr? I don't see how.
I 'm very bad in english, sorry.
Here is a
dm.maillists:
On Thursday 05 July 2007 11:20, Michael Vanier wrote:
Again, I'm sure this has been done before (and no doubt better); I'd
appreciate any pointers to previous work along these lines.
Takusen is, if I recall correctly, based around a generalised fold supporting
accumulation
On 05/07/2007, at 10:08 AM, Michael Vanier wrote:
Can you do dropWhile in terms of foldr? I don't see how.
Mike
I considered that very question in an article I wrote for the
Monad.Reader magazine:
http://www.haskell.org/sitewiki/images/1/14/TMR-Issue6.pdf
If you are really keen,
10 matches
Mail list logo
