Cagdas Ozgenc [EMAIL PROTECTED] wrote:
Greetings,
Is identity function the only meaningful function one can write
without constraining the type variable using a typeclass? If not,
could you please give a counter-example?
Certainly you can write lots of ``meaningful function''s
Greetings,
1) How does one model out of memory condition in Haskell, perhaps
using a Maybe type?
Unfortuntely not since it would not be referentially transparent. It's
part of a more general issue of exceptions in pure code.
You can't have
calculateSomething :: X - Maybe Y
Such
I did not mean to include functions that take type constructors as
parameters (so lists are out of my discussion scope). I am only considering
functions that uses type variables that are not restricted by typeclasses.
There is const:
const :: a - b - a
const x _ = x
And of course a
Does this make the use of Monads doubtful? I mean it doesn't seem easy to
have a completely pure language, and the time one starts introducing few
impurities one also starts thinking why not include many others?
I suggest that you read this paper:
A semantics for imprecise exceptions,
I did not mean to include functions that take type constructors as
parameters (so lists are out of my discussion scope). I am only
considering
functions that uses type variables that are not restricted by
typeclasses.
There is const:
const :: a - b - a
const x _ = x
And of
On Monday, 2003-03-03, 10:00, CET, Cagdas Ozgenc wrote:
[...]
I did not mean to include functions that take type constructors as
parameters (so lists are out of my discussion scope). I am only considering
functions that uses type variables that are not restricted by typeclasses.
In this
My three eurocents.
I believe that the Author of the original query won't care more about
undefined stuff than most of us. He wants truly polymorphic functions,
of the type, say, a-b-a etc., without constraints.
The answer exists, although it is not always trivial to find interesting
Hello. I'm running into a problem with the Network module, which I suspect
is pretty easy to fix, but am not sure how to best do so.
The problem is that accept fails when the reverse DNS fails, with the
following error:
Fail: does not exist
Action: getHostByAddr
Reason: no such host entry
I'm
So, I'm having to calculate 'n choose k' an awful lot. At the moment I've got
this:
comb :: Integer - Integer - Integer
comb m 0 = 1
comb m n = (numerator(toRational (fact m) / toRational (fact n * fact (m-n
where fact is a memoized factorial function. It's not perfectly memoized,
I think you would get a big speed-up if you got rid of all the rational
stuff and just used:
comb m n = fact m `div` (fact n * fact (m-n))
If that doesn't speed it up enouch, you can of course cache fact m in your
computation and do something like:
sumbn n = sum [ bournoulli i * fm `div` (fn *
On Tuesday, March 4, 2003, at 10:26 AM, Damien R. Sullivan wrote:
So, I'm having to calculate 'n choose k' an awful lot. At the moment
I've got
this:
comb :: Integer - Integer - Integer
comb m 0 = 1
comb m n = (numerator(toRational (fact m) / toRational (fact n * fact
(m-n
where fact is
G'day all.
On Mon, Mar 03, 2003 at 04:59:21PM -0800, Hal Daume III wrote:
I think you would get a big speed-up if you got rid of all the rational
stuff and just used:
comb m n = fact m `div` (fact n * fact (m-n))
Or, even better, if you didn't multiply stuff that you're just going
to
I have no idea if the following is faster or not (I suspect not), but
it is certainly easier to read:
n `choose` k = (n `permute` k) `div` (fact k)
n `permute` k = product [(n-k+1) .. n]
fact n = product [1 .. n]
mike
--
mike castleman / [EMAIL PROTECTED] / http://mlcastle.net
aolim: mlcastle
On Tue, Mar 04, 2003 at 12:25:01PM +1100, Andrew J Bromage wrote:
Or, even better, if you didn't multiply stuff that you're just going
to divide out in the first place.
I had thought of that before, and used a simple
comb m n = product [m, m-1 .. m-n+1] / fact (m-n)
but the unmemoized product
On Mon, Mar 03, 2003 at 04:59:21PM -0800, Hal Daume III wrote:
comb m n = fact m `div` (fact n * fact (m-n))
This was the biggest help, 33 seconds instead of my original 43. fact is the
big consumer now, and I think cries out for being arrayed, especially as it
gets used a lot elsewhere too.
main =
do
args - System.getArgs
let (m, b) = (read (args!!0), read (args!!1))
let lim :: Int
lim = read (args!!2)
printstate = args!!3
time1 - getClockTime
let n = 2^b
let afact = array (0,n) ((0,1):[(i,i*afact!(i-1)) |
On Tue, Mar 04, 2003 at 03:06:13PM +1100, Bernard James POPE wrote:
Damien writes:
main =
do
args - System.getArgs
let (m, b) = (read (args!!0), read (args!!1))
let lim :: Int
lim = read (args!!2)
printstate = args!!3
Hi,
For the reason that I'm lazy and don't want to have to modify all my functions
which use afact, or call functions which use afact, and don't see why I should
have to -- they were able to call the 'fact' function as a global, and can
refer to a global 'afact' if I define it outside of main
On Mon, Mar 03, 2003 at 10:45:38PM -0600, Jon Cast wrote:
Never programmed in C++ much, eh?
Only for a few years, professionally.
In general, getting the ordering of initialization right in the general
case is a harder problem than you might think.
It's not something I'd be having trouble
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