G'day all.
Quoting Matthew Brecknell [EMAIL PROTECTED]:
Yes. Function application (-) is right-associative in a type
expression. What about a value expression?
f a b === (f a) b
Looks like an inconsistency? Not if you think about it. :-)
And if you don't want to think about it, this
pphetra:
I would like to write a program that can do something like this.
;; lisp syntax
* (my-flatten '(1 (2 (3 4) 5)))
(1 2 3 4 5)
I end up like this.
data Store a = E a | S [Store a]
deriving (Show)
flat :: [Store a] - [a]
flat [] = []
flat ((E x):xs) = [x] ++
On Fri, Dec 29, 2006 at 03:36:45AM -0500, [EMAIL PROTECTED] wrote:
And if you don't want to think about it, this should make everything
clear:
f :: A - (B - (C - D))
f a :: B - (C - D)
(f a) b :: C - D
((f a) b) c :: d
Nice illustration. It's as if the letters jumped over
On Fri, Dec 29, 2006 at 07:58:54PM +1100, Donald Bruce Stewart wrote:
Since this data type:
data Store a = E a | S [Store a]
deriving (Show)
Is isomorphic to the normal Data.Tree type anyway, so we'll use that:
It's a bit different - store has labels only in its leaves.
Hi
f1 :: [Int] - [[Int]]
f1 [] = []
f1 (a:as) = [a] : f1 as
f1 is simply a map
f3 la lb = let a = head la
b = head lb
in if sum a = sum b then
a : f3 (tail la) lb
else
On Thu, Dec 28, 2006 at 11:56:58PM -0800, pphetra wrote:
data Store a = E a | S [Store a]
deriving (Show)
flat :: [Store a] - [a]
flat [] = []
flat ((E x):xs) = [x] ++ flat xs
flat ((S x):xs) = flat x ++ flat xs
so
*Main flat [E 1, S[E 2, S[E 3, E 4], E 5]]
[1,2,3,4,5]
GHC is simply being more conservative. GHC 6.4.2 was straying too close to
non-termination, as our paper shows:
http://research.microsoft.com/~simonpj/papers/fd-chr
Simon
| -Original Message-
| From: [EMAIL PROTECTED] [mailto:haskell-cafe-
| [EMAIL PROTECTED] On Behalf Of
Hello Steve,
Friday, December 29, 2006, 5:41:40 AM, you wrote:
then I can't avoid naming and using an intermediate variable. And that
annoys me. The u in process2 is of no more value to me (pardon the
pun) as the one in process1, but I am forced to use it simply because
the data flow is no
Hello Grady,
Friday, December 29, 2006, 10:12:12 AM, you wrote:
not get that in the way I want. I suppose there may have to be some
slowdown -- if the compiler specializes every piece of code for every
instance of a typeclass it might encounter, it could bloat the
executable beyond all
Hi
pphetra wrote:
Compare to a Lisp solution, It 's not looking good.
Any suggestion.
I'm trying to understand what your issue is here. What's not looking
good?
I would like to write a program that can do something like this.
;; lisp syntax
I suppose, if it were the implementation of
On 12/29/06, Conor McBride [EMAIL PROTECTED] wrote:
Or is your issue more superficial? Is it just that
* (my-flatten '(1 (2 (3 4) 5)))
(1 2 3 4 5)
looks shorter than
so
*Main flat [E 1, S[E 2, S[E 3, E 4], E 5]]
[1,2,3,4,5]
Speaking as a relative newbie to Haskell, the thing that
On Fri, Dec 29, 2006 at 02:06:32PM +, Paul Moore wrote:
Speaking as a relative newbie to Haskell, the thing that tripped me up
was the fact that you can't have nested lists like the Lisp '(1 (2 (3
4) 5)) example in Haskell, because its type is not well-defined.
More precisely: You can't
On 12/29/06, Bulat Ziganshin [EMAIL PROTECTED] wrote:
i propose you to use INLINE pragma:
{-# INLINE foo #-}
unless your function is recursive. in this case, you should use SPECIALIZE
pragma:
{-# SPECIALIZE foo :: Double - Double - Double #-}
I suggest *not* using these pragmas unless a
Steve Schafer wrote:
Here's the essence of the problem. If I have this:
process1 x y =
let u = foo x y;
v = bar u;
w = baz v
in w
I can easily rewrite it in point-free style:
process1 = baz . bar . foo
Not unless you have a much fancier version of
On Fri, 29 Dec 2006 09:01:37 -0800, you wrote:
Steve Schafer wrote:
I can easily rewrite it in point-free style:
process1 = baz . bar . foo
Not unless you have a much fancier version of function composition,
like...
http://okmij.org/ftp/Haskell/types.html#polyvar-comp
Sorry; I
On Fri, 29 Dec 2006 14:23:20 +0300, you wrote:
it force you to give names to intermediate results which is considered as
good programing style - program becomes more documented.
But that would imply that function composition and in-line function
definition are also Bad Style.
Steve Schafer
On Tue, Dec 26, 2006 at 09:56:11PM -0500, Steve Schafer wrote:
But that isn't quite the case. Each step consumes not only the results
of the previous step, but also some combination of the results of
prior steps and/or the original inputs. One way to look at this is a
directed graph, a sort of
To get another perspective, let's eliminate some unnecessary naming and see
what linear pipelines emerge:
process item mediaKind mediaSize language =
let (numberedQuestions,questionCategories) =
numberQuestions pagemaster $
stripUndisplayedQuestions mediaKind $
Conal Elliott wrote:
Warning: I haven't tried to type-check and may have made a clerical error.
Since questionCategories isn't used, use fst eliminate another let.
Then, for my personal preference, and just to mix things up, switch to
where style:
process item mediaKind mediaSize language
Hi Quan
I am not sure how to express f1 with map? how do I say
(lambda (ls)
(map (lambda (x) (list x))
ls))
in Haskell? map ([]) ?
map (:[]), :[] takes a single element and puts it into a list. Some
people refer to this as box
The final f3 clause can be made a bit neater:
f3
Sorry to Neil for multiple copies.
On 29/12/06, Neil Mitchell [EMAIL PROTECTED] wrote:
I am not sure how to express f1 with map? how do I say
(lambda (ls)
(map (lambda (x) (list x))
ls))
in Haskell? map ([]) ?
map (:[]), :[] takes a single element and puts it into a list. Some
I am not sure how to express f1 with map? how do I say
(lambda (ls)
(map (lambda (x) (list x))
ls))
in Haskell? map ([]) ?
map (:[]), :[] takes a single element and puts it into a list. Some
people refer to this as box
Another way to express f1 with map is:
f1 xs = map (\x -
I've performed some experiments in GHCi, and it looks like even for a
simple function (+) (which should be the worst case, since if the
computation is simple, any extra time required to dispatch the call
will show up more strongly in comparison) it doesn't really matter. I
get essentially the
I assume that your proper goal is not to structure pipeline processes
in full generality, but to simplify the current one at hand.
No, I'm looking for full generality. ;)
I have dozens of these kinds of quasi-pipelines, all similar in
overall appearance, but different in detail.
Ah, the
On 12/29/06, Neil Mitchell [EMAIL PROTECTED] wrote:
map (:[]), :[] takes a single element and puts it into a list. Some
people refer to this as box
The final f3 clause can be made a bit neater:
f3 la@(a:as) lb@(b:bs) | sum a = sum b = a : f3 as lb
|
On 29/12/06, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
And if you don't want to think about it, this should make everything
clear:
My additions displayed below:
f :: A - B - C - D
f :: A - (B - (C - D))
By right-associativity of f.
f a :: B - (C - D)
(f a) b :: C - D
((f
Before you start adding pragmas, try compiling with -O, it does a lot
of the specialization automatically.
-- Lennart
On Dec 29, 2006, at 15:00 , Grady Lemoine wrote:
I've performed some experiments in GHCi, and it looks like even for a
simple function (+) (which should be the worst
I'm thinking around the design of a couple of things, and am hitting
an issue which I know how I would solve in Python, but I'm not sure
what a good idiomatic Haskell approach would be.
The problem is that I am trying to write a function which takes a
rather large number of arguments, many of
Hi Paul,
To make things concrete, the example I'm really thinking of is a send
an email function, which would take a subject, a body, a list of
recipients, optional lists of cc and bcc recipients, an optional
mailserver (default localhost), an optional port (default 25), and
possibly optional
On 29/12/06, Paul Moore [EMAIL PROTECTED] wrote:
I looked at wxHaskell for inspiration - its approach (button f [text
:= Quit, on command := close f]) looks quite readable, but slightly
unusual (to me) for Haskell. It also seems fairly complex to implement
(ie, my head hurt when I tried to
On 29/12/06, Paul Moore [EMAIL PROTECTED] wrote:
I looked at wxHaskell for inspiration - its approach (button f [text
:= Quit, on command := close f]) looks quite readable, but slightly
unusual (to me) for Haskell. It also seems fairly complex to implement
(ie, my head hurt when I tried to
Hello,
breakUp s
| L.null s = []
| otherwise = h:(breakUp r) where
(h,r) = L.splitAt 72 s
Running this on the 2G file blows up the stack pretty quickly, taking
the first 1 million records (there are 20M of them) with a big stack
parameter gives about 25%
Steve Schafer wrote:
Here's the essence of the problem. If I have this:
process1 x y =
let u = foo x y;
v = bar u;
w = baz v
in w
I can easily rewrite it in point-free style:
process1 = baz . bar . foo
That should have been
process1 = (.) (baz . bar) . foo
On Fri, Dec 29, 2006 at 04:56:34PM -0800, Ranjan Bagchi wrote:
I'm loading a big file (~2G), again, with 72-byte C structs. I've
done pretty well [thanks to everyone] interpreting the fields, but
I'm finding the traversal of the file to be pretty inefficient.
breakUp s
| L.null s
Hi,
I'm reading the Haskell school of expression by Paul Hudok. Great book.
However I would like some feedback about a solution to an exercise
The problem is quite simple :
define f1 and f2 (using higher order functions ) such that
f1 (f2 (*) [1..4]) 5 = [5,10,15,20]
I have come up with the
breakUp s
| L.null s = []
| otherwise = h:(breakUp r) where
(h,r) = L.splitAt 72 s
Running this on the 2G file blows up the stack pretty quickly, taking
the first 1 million records (there are 20M of them) with a big stack
parameter gives about 25%
On 30/12/2006, at 1:33 PM, Pieter Laeremans wrote:
Hi,
I'm reading the Haskell school of expression by Paul Hudok. Great
book.
Hudak. And I concur, a great book.
However I would like some feedback about a solution to an exercise
The problem is quite simple :
define f1 and f2 (using
On 30/12/2006, at 1:32 PM, Matthew Brecknell wrote:
In my (limited) Haskell experience, I was continually being
surprised by
inexplicable stack blowouts until I spent a little time doing some
focussed experiments, mainly involving folds over large lists. If you
haven't done that, I would
Paul Moore wrote:
I'm thinking around the design of a couple of things, and am hitting
an issue which I know how I would solve in Python, but I'm not sure
what a good idiomatic Haskell approach would be.
The problem is that I am trying to write a function which takes a
rather large number of
On Dec 29, 2006, at 6:32 PM, Matthew Brecknell wrote:
breakUp s
| L.null s = []
| otherwise = h:(breakUp r) where
(h,r) = L.splitAt 72 s
Running this on the 2G file blows up the stack pretty quickly, taking
the first 1 million records (there are 20M of them)
I'm trying to wrap my mind around the darcs source code as a preliminary
to looking into GHC's guts. All of darcs is written as .lhs files which
have bizarre mark-up in them which distracts me from the actual Haskell
source I'm trying to figure out and get used to. Apparently the GHC
compiler
On 30/12/06, Ranjan Bagchi [EMAIL PROTECTED] wrote:
I guess the consumer's really important (Didn't even occur to me, I
was concentrating on how I was generating the list).
I was trying to de-lazy the list, I did the following:
bs = [...]
recs' = (take 100) breakUp bs
recs = foldr seq recs'
On 30/12/06, Michael T. Richter [EMAIL PROTECTED] wrote:
I'm trying to wrap my mind around the darcs source code as a preliminary to looking into
GHC's guts. All of darcs is written as .lhs files which have bizarre mark-up in them
which distracts me from the actual Haskell source I'm trying
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