Mark P Jones wrote:
Moreover,
in attempting to optimize the code, you might instead break it
and introduce some bugs that will eventually come back and bite.
Indeed! If we take Mark Phillips's original version of penultimax as our
specification, all four alternate versions are incorrect:
On Sun, Nov 24, 2002 at 10:06:42PM -0800, Mark P Jones wrote:
To your three implementations, let me add another two. If you are
looking
for the smallest possible definition, consider the following:
import List
penultimax1 :: Ord a = [a] - a
penultimax1 = head . tail . sortBy
Some quick tests with Hugs +s on a example list that I constructed
with 576 elements give food for thought:
reductions cells
my one liner 403511483
tournament705312288
your penultimax 1671520180
your
Thanks for your alternative solutions. (I also take
Mark Jones' point that there was an error with some of my
initial solutions.)
On Mon, 2002-11-25 at 16:36, Mark P Jones wrote:
To your three implementations, let me add another two. If you are
looking
for the smallest possible definition,
On Tue, 2002-11-26 at 02:38, Richard Braakman wrote:
penultimax1' :: Ord a = [a] - a
penultimax1' = head . tail . sortBy (flip compare) . nub
What does nub stand for? (This is the first I've heard of it.)
From the definition in List.hs it seems to remove repeats, keeping
only the first. Is
Subject: RE: Best recursion choice for penultimax
Hi Mark,
| I have just implemented the function penultimax which takes a list
| of positive integers and produces the penultimate maximum, that is,
| the next biggest integer in the list after the maximum. Eg:
|
| penultimax [15,7,3,11,5] = 11
What does nub stand for? (This is the first I've heard of it.)
From the definition in List.hs it seems to remove repeats, keeping
only the first.
Yes, that's what it does. It doesn't stand for anything, it's a word:
nub: small knob or lump, esp. of coal; small residue, stub; point or gist
Hi Mark,
| I have just implemented the function penultimax which takes a list
| of positive integers and produces the penultimate maximum, that is,
| the next biggest integer in the list after the maximum. Eg:
|
| penultimax [15,7,3,11,5] = 11
To your three implementations, let me add another
