On Sat, Jan 1, 2011 at 8:54 AM, Felipe Almeida Lessa

wrote:

On Fri, Dec 31, 2010 at 6:43 PM, aditya siram wrote:

...

-- untested and won't work on an infinite list last :: [a] -> a last = head . reverse

No definition for last works with infinite lists =).

Unless you make the result nullable, of course. maybeLast :: [a] -> Maybe a maybeLast [] = Nothing maybeLast [x] = Just x maybeLast (_:xs) = maybeLast xs

Cheers,

-- Felipe.

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On Sat, Jan 1, 2011 at 8:39 PM, Henning Thielemann < lemming@henning-thielemann.de> wrote:

On Sat, 1 Jan 2011, Jesse Schalken wrote:

On Sat, Jan 1, 2011 at 8:54 AM, Felipe Almeida Lessa <

...

felipe.lessa@gmail.com> wrote:

...

No definition for last works with infinite lists =).

Unless you make the result nullable, of course.

maybeLast :: [a] -> Maybe a

maybeLast [] = Nothing

maybeLast [x] = Just x maybeLast (_:xs) = maybeLast xs

How would this work for infinite lists?

If your list is infinitely big, then reaching its end will take infinitely long. ;) It will loop forever, just like `last [1...]` does.

On Sat, 2011-01-01 at 19:27 +1100, Jesse Schalken wrote:

On Sat, Jan 1, 2011 at 8:54 AM, Felipe Almeida Lessa wrote: On Fri, Dec 31, 2010 at 6:43 PM, aditya siram wrote: > -- untested and won't work on an infinite list > last :: [a] -> a > last = head . reverse

No definition for last works with infinite lists =).

Unless you make the result nullable, of course.

maybeLast :: [a] -> Maybe a

maybeLast [] = Nothing maybeLast [x] = Just x maybeLast (_:xs) = maybeLast xs

It may or may not be expected but it may also be written as: maybeLast' [] = Nothing maybeLast' (x:xs) = Just (fromMaybe x (maybeLast xs)) The main differences are: maybeLast (x:_|_) = _|_ maybeLast' (x:_|_) = Just _|_ maybeLast (fix (x:)) = _|_ maybeLast' (fix (x:)) = Just _|_ Regards

On Sat, 2011-01-01 at 19:27 +1100, Jesse Schalken wrote:

On Sat, Jan 1, 2011 at 8:54 AM, Felipe Almeida Lessa wrote: On Fri, Dec 31, 2010 at 6:43 PM, aditya siram wrote: > -- untested and won't work on an infinite list > last :: [a] -> a > last = head . reverse

No definition for last works with infinite lists =).

Unless you make the result nullable, of course.

maybeLast :: [a] -> Maybe a

maybeLast [] = Nothing maybeLast [x] = Just x maybeLast (_:xs) = maybeLast xs

It may or may not be expected but it may also be written as: maybeLast' [] = Nothing maybeLast' (x:xs) = Just (fromMaybe x (maybeLast xs)) The main differences are: maybeLast (x:_|_) = _|_ maybeLast' (x:_|_) = Just _|_ maybeLast (fix (x:)) = _|_ maybeLast' (fix (x:)) = Just _|_ Regards

On 31 December 2010 20:44, Matthew Steele wrote:

Sounds like you're looking for `last', which is in the Prelude.

Yep, feeling dumb I did not try it ! Thanks, Aaron

http://www.haskell.org/ghc/docs/6.12.2/html/libraries/base-4.2.0.1/Prelude.h...

Cheers, -Matt

On Dec 31, 2010, at 3:39 PM, Aaron Gray wrote:

Is there an easy Haskell function that gets the last Char of a [Char] or

...

String ?

Many thanks in advance,

Aaron

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