Jose A.Ortega Ruiz wrote:
as stated in the subject, i'm a newcomer to haskell programming: i've
read some tutorials and (portions of) a couple of books and am really
fascinated with the language. but my haskell coding experience is
limited to toy programs and short exercises. so i decided to
On Wed, 13 Aug 2003 13:26:34 +0200
blaat blaat [EMAIL PROTECTED] wrote:
I have a long reply, perhaps I'll post it later. Here's a more
pragmatic short one.
What did we lose? Well, introspection comes to mind. A monad is
strange in the sense that, actually, there does not seem to be any
Tim Stitt wrote:
I'm using the Helium interpreter/compiler with the Hint interface within
Linux. Unfortunately, I want an editor that allows me to jump to the
row/column of the source when I receive an error.
Does anyone know of a good editor in Linux to do this or the commands for
Emacs
Ketil Z. Malde wrote:
Antony Courtney [EMAIL PROTECTED] writes:
-- Example: format a list of strings, using a comma as a seperator:
mkSepStr :: [String] - String
mkSepStr xs = foldrs (\x s - x ++ , ++ s) xs
t0 = mkSepStr [] -- ==
t1 = mkSepStr [hello]-- == hello
On Tuesday 05 August 2003 15:23, Wolfgang Jeltsch wrote:
There probably are ways to achieve this with Haskell's type system. The
exact solution depends on what exactly you want.
For just distinguishing between lists of different lengths you could use
tuples like (a,a) (list of length 2)
Dnia pon 11. sierpnia 2003 00:49, Wolfgang Jeltsch napisa:
The main problem is that you need binary I/O. Haskell 98 only provides text
I/O.
You don't need binary I/O for UTF-8 now; because implementations use
ISO-8859-1, UTF-8 octets can be faked as characters by (chr . fromIntegral).
The
On Thu, 14 Aug 2003, Wolfgang Jeltsch wrote:
On Thursday, 2003-08-14, 17:05, CEST, Kevin S. Millikin wrote:
On Wednesday, August 13, 2003 11:20 PM, Tn X-10n
[SMTP:[EMAIL PROTECTED] wrote:
is it possible to convert IO Bool to Bool?
Sure. Which Bool do you want? True?
toTrue
Antony Courtney [EMAIL PROTECTED] writes:
-- Example: format a list of strings, using a comma as a seperator:
mkSepStr :: [String] - String
mkSepStr xs = foldrs (\x s - x ++ , ++ s) xs
t0 = mkSepStr [] -- ==
t1 = mkSepStr [hello]-- == hello
t2 = mkSepStr
Hey there!
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[EMAIL PROTECTED] wrote:
If I may interject, that's precisely how a Scheme DB interface is
designed. The main function is a left-fold. Not quite though: it
provides for a premature termination:
A major procedure: DB1:fold-left PROC INITIAL-SEED QUERY-OBJECT
Premature termination sounds
[String] contains = ["1 0 0","1 0 0","0 1 0"] this [String] is read from a file.
the file shows only: i convert it by using Lines. but i stuck wif the output.
1 0 0
1 0 0
1 0 1
if 1 then False 0 then True
the expected result show be [[False,True,True],[False,True,True],[True,False,True]]
My code
On Tuesday, 2003-08-05, 15:22, CEST, Nick Name wrote:
[...]
Is there any way to parametrize a type by a value, rather than another
type? What I would like to do is to define list of length 3 and list of
length 4 as separate parametrization of the same type, such that I could
write
Alistair,
Hhhmmm. That is an interesting issue, and I am unsure how to treat it
in the tutorial. I did attempt to explain the ability of the monad to
isolate impure computations, but I think I need to make a better
explanation of what an action is and how it is used.
As for the question of
To many questions, not enough mail. First, thanks for all your replies.
Second, I stand totally corrected on the fact that we cannot break down
monads. Functions of type m a-b are called impure, see also
unsafePerformIO. I am questioning (a) the exact relation between monads,
monadic IO, IO in
Peter G. Hancock wrote:
Jeff Newbern wrote (on Tue, 12 Aug 2003 at 17:20):
?
The functions exported from the IO module do not
perform I/O themselves. They return I/O actions, which describe an I/O
operation to be performed. The I/O actions are combined within the IO
monad (in a
The overall message I have taken from your post is that I need to
be more precise to convey the correct information and avoid confusion
(or worse, misinformation).
As I understood it, the tutorial should be instructive. So I would not
try to be more precise at the beginning, because too much
I'll probably generalise the query function to do a fold, rathen than
always accumulate a list:
doquery :: Process - String - (a - b - IO b) - b - IO b
If I may interject, that's precisely how a Scheme DB interface is
designed. The main function is a left-fold. Not quite though: it
I suspect that tutorials should at some point mention some
definitions of monads, monoids et al --- since this is where the power
(sorry, QA) comes from.
I was reading an overview-for-non-specialists of category theory earlier
today, and was surprised by the familiarity of much of it - based
i am new wif haskell, i would like to know how can i get a list of string and
convert it to a list of a list of bool
[String]- [[Bool]]
for example a [String] [0 1 0 1 0 1,0 0 0 0 0 0 ,1 0 0 0 1 0]
it return true if 0 and false if 1. the [String] is read from a
file.
map (\x - map
hi all,
as stated in the subject, i'm a newcomer to haskell programming: i've
read some tutorials and (portions of) a couple of books and am really
fascinated with the language. but my haskell coding experience is
limited to toy programs and short exercises. so i decided to try my
hand at a
Peter,
Thank you for criticism. This is exactly the kind of feedback I need.
The overall message I have taken from your post is that I need to
be more precise to convey the correct information and avoid confusion
(or worse, misinformation).
I should have said that a function which performs a
On Tuesday, 2003-08-05, 15:22, CEST, Nick Name wrote:
snip
This is called dependent types and is not a feature of haskell
(nor of any language that I know); there was cayenne (try a google
search) but I don't believe it is still mantained.
snip
BTW, why is there no general interest
On Thursday 14 August 2003 06:20, Tn X-10n wrote:
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From: Derek Elkins [EMAIL PROTECTED]
blaat blaat [EMAIL PROTECTED] wrote:
[...]
However, given that observation, the fact that IO is a monad I find to
be a _rather arbitrary design decision_; why not define a small term
language which may be passed to the OS?
That would be confusing to use or
hey there, i thought you'd like to check this out
You really owe it to yourself and your family to take a look,
With the money you save, put it towards a new car!
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Hello,
I have put up all-in-one archives of the tutorial for people who
prefer to read it offline.
http://www.nomaware.com/monads/monad_tutorial.tgz
and
http://www.nomaware.com/monads/monad_tutorial.zip
Thanks,
Jeff Newbern
[EMAIL PROTECTED]
__
Do you Yahoo!?
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
I still want to use HaskellDB (or at least the relational calculus part of
it), so I was thinking of splitting it into two pieces: a library that
submits SQL queries and returns the results (database interface), and a
library that constructs
On Thursday, 2003-08-14, 17:05, CEST, Kevin S. Millikin wrote:
On Wednesday, August 13, 2003 11:20 PM, Tn X-10n
[SMTP:[EMAIL PROTECTED] wrote:
is it possible to convert IO Bool to Bool?
Sure. Which Bool do you want? True?
toTrue :: IO Bool - Bool
toTrue x = True
Or False?
On Tue, Aug 12, 2003 at 03:04:39PM -0400, Antony Courtney wrote:
So then, in your view, what *is* an IO action?
One conceptual model is that an IO action with type (IO a) denotes a
function of type World - (World,a).
But the IO monad is not a state monad, because other agents may change
the
On Wednesday, August 13, 2003 11:20 PM, Tn X-10n
[SMTP:[EMAIL PROTECTED] wrote:
is it possible to convert IO Bool to Bool?
Sure. Which Bool do you want? True?
toTrue :: IO Bool - Bool
toTrue x = True
Or False?
toFalse :: IO Bool - Bool
toFalse x = False
Maybe that's not what you had
From: Wolfgang Jeltsch [mailto:[EMAIL PROTECTED]
For example, the function readFile is pure. For a specific
string s the
expression readFile s always yields the same result: an I/O
action which
searches for a file named s, reads its content and takes this
content as the
result of
PBRhai guys/Pis it possible to convert IO Bool to Bool?
No, it's not... and for good reason! See the discussion at
http://www.haskell.org/hawiki/ThatAnnoyingIoType
and
http://www.haskell.org/hawiki/UsingIo
In general, the HaWiki has answers to lots of newbie questions like
this - you might
On Thursday, 2003-08-14, 07:20, CEST, Tn X-10n wrote:
hai guys
is it possible to convert IO Bool to Bool?
No. The reason for introducing the IO type is to preserve the purity of
Haskell, i.e., to ensure that expression evaluation doesn't depend on the
state of the outside world and doesn't
On Wed, 13 Aug 2003 09:44:36 +0200
blaat blaat [EMAIL PROTECTED] wrote:
Hmmm, I personally always thought of the IO monad as being a synonym
for Program
So. What is a Program?
[...]
For what is the interpretation of an object of type IO a? Well, it is
a bit of a hack atop of Haskell,
a string is a list of Char which can be '1', '0', '/n'and spaces ' '. ["1 0 1 0 0 1 /n"]Get free gift vouchers every week with MSN Premium Vouchers
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Hmmm, I personally always thought of the IO monad as being a synonym for
Program (or, for functions wich return an IO a, a subroutine with
side-effects which returns a value of type a).
We can build mini programs (like putStr), and compose them in a sequential
manner (including something alike
Tim Docker writes:
| Tom Pledger writes:
|
| This is a pretty good way to stop those nasty vague SQL row types at
| the Haskell border and turn them into something respectable. Perhaps
| it would even be worth constraining the extracted type to be in
| DeepSeq
|
| doquery
hi,
Jose A.Ortega Ruiz wrote:
hi all,
as stated in the subject, i'm a newcomer to haskell programming: i've
read some tutorials and (portions of) a couple of books and am really
fascinated with the language. but my haskell coding experience is
limited to toy programs and short exercises. so i
Thomas L. Bevan writes:
| Does anyone know if there is work being done on a standard Haskell
| database interface.
I suspect that there isn't. The pattern seems to be that someone gets
an interface working well enough for some purposes, and perhaps shares
it, but is too modest and/or busy to
Tom Pledger writes:
This is a pretty good way to stop those nasty vague SQL row types at
the Haskell border and turn them into something respectable. Perhaps
it would even be worth constraining the extracted type to be in
DeepSeq
doquery :: (DeepSeq v) =
Process -
Tn X-10n [EMAIL PROTECTED] writes:
change :: String - Bool
change 1 = True
change 0 = False
conv :: [String] - [Bool]==unable to declare [[Bool]]
Again: a String is a list of ?
-kzm
--
If I haven't seen further, it is by standing in the footprints of giants
Tn X-10n [EMAIL PROTECTED] writes:
i am new wif haskell, i would like to know how can i get a list of
string and convert it to a list of a list of bool
[String]- [[Bool]]
What is the definition of a String? (I.e. what is a String a list of?)
Write a function to convert one of these to the
-Original Message-
From: Jeff Newbern [mailto:[EMAIL PROTECTED]
Alistair,
Hhhmmm. That is an interesting issue, and I am unsure how to treat it
in the tutorial. I did attempt to explain the ability of the monad to
isolate impure computations, but I think I need to make a better
-Original Message-
From: Thomas L. Bevan [mailto:[EMAIL PROTECTED]
This type of interface is fine as far as it goes, but there is only
ever a loose coupling between the database and application.
The HaskellDB work implemented a relational calculus that ensured
that all queries
Alistair,
Thanks for your message regarding the debate about monads and purity.
What do you think about these additions as a discussion of the issue?
Does this address everything you think is needed? Is there a clearer
way to explain it?
Thanks,
Jeff
In the section No Way Out:
--
The
I think the crucial distinction is to think about is the difference
between calculating a value (such as a character) compared to calculating
an action (such as a computation that reads a character) --- one is wholly
in your programming language while the other interacts with something
outside
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Hi,
We try to make a program which write on stdout the UTF-8 character
corresponding to an input unicode value. And this under MacOS X,
Debian linux, and Windows.
It seems to be easy, but we can't have found anything valuable, on
the net.
Would you mind to help us?
Niko.
Ps: excuse my poor
I have a program which creates textfiles out of other
files. Since theprogram is runned from windows I output some text strings
(Like "Filecreated succefully") and I need to stop the program before it
quits so thatthe user can read the line outputted to know what went on and
then he canpress
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