On Thursday, 2003-08-14, 13:37, CEST, blaat blaat wrote:
> [...]
Hello,
I don't know exactly which of the following questions have already been
answered but I decided to answer them all anyway.
> What is the difference between putStr "a", (putStr "a", putStr "a"), putStr
> (putStr "a"), putStr
On Thu, 14 Aug 2003, blaat blaat wrote:
>
> 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,
Haskell is a pure language, so there are *no* impu
Hi all,
I've been following this discussion with some interest.
Last time I looked, hugs, ghc and nhc98 all implemented
I/O differently. No doubt there are even more
alternatives in other Haskell implementations (real or imaginary).
In itself this is probably not too surprising. They are, after
On Tuesday, 2003-08-12, 12:14, CEST, Alistair Bayley wrote:
> [...]
> > Care to explain why you think Haskell is not pure?
>
> Purely functional = you are always defining and calling pure functions.
> Calling a pure function with the same arguments always gives the same
> results. In Haskell, if
Hello everyone,
Due to the scarcity of monad tutorials available (:^), I have
written one of my own. I hope that this one is both more gentle
and more comprehensive than many of the other tutorials out on
the 'net, and I am looking for feedback from experienced
Haskellers and novices alike.
You
ld at some point mention some
definitions of monads, monoids et al --- since this is where the power
(sorry, QA) comes from.
Phil
On Tue, 12 Aug 2003, Bayley, Alistair wrote:
> Date: Tue, 12 Aug 2003 12:10:24 +0100
> From: "Bayley, Alistair" <[EMAIL PROTECTED]>
> Subj
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
> -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
> Jeff Newbern wrote (on Tue, 12 Aug 2003 at 17:20):
(proposed revisions)
> In the section "No Way Out":
> --
> The IO monad is a familiar example of a one-way monad in Haskell.
> Because you can't escape from the IO monad, it is impossible to write a
> function th
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 al
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
> Think of the following though experiment. What if I would have a function
> "unparse:IO a->String" which gives the textual representation of the
> specification of the object of type IO a? Clearly, IO is not a monad
> anymore. Moreover, I don't think it would break the purity of Haskell. And
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 t
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 co
hello,
sorry for asking so many questions :-)
blaat blaat wrote:
...
Hmmm, uhm, but let's think further...
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 reason to
compute its value since we cannot possibly get
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!?
> "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?
Derek Elkins <[EMAIL PROTECTED]> writes:
> That would be
> 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
> 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
> res
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 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
On Tuesday, 2003-08-12, 18:20, CEST, Jeff Newbern wrote:
> [...]
> In the section "No Way Out":
> --
> The IO monad is a familiar example of a one-way monad in Haskell. Because
> you can't escape from the IO monad, it is impossible to write a function
> that does a computation in the IO mo
> Hello everyone,
>
> Due to the scarcity of monad tutorials available (:^), I have
> written one of my own. I hope that this one is both more gentle
> and more comprehensive than many of the other tutorials out on
> the 'net, and I am looking for feedback from experienced
> Haskellers and novice
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 (i
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
On Tue, 12 Aug 2003 23:15:30 +0200
Wolfgang Jeltsch <[EMAIL PROTECTED]> wrote:
> On Tuesday, 2003-08-12, 18:20, CEST, Jeff Newbern wrote:
> > [...]
>
> > In the section "No Way Out":
> > --
> > The IO monad is a familiar example of a one-way monad in Haskell.
> > Because you can't escape
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 whet
ECTED]
> Sent: 12 August 2003 10:41
> To: [EMAIL PROTECTED]
> Subject: Yet Another Monad Tutorial
>
>
> Hello everyone,
>
> Due to the scarcity of monad tutorials available (:^), I have
> written one of my own. I hope that this one is both more gentle
> and m
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
>
On Tuesday, 2003-08-12, 13:10, Alistair Bayley wrote:
> > 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, re
Definitely the most comprehensive monads tutorial on the net.
Great stuff!
Thanks,
Peter
On Tuesday 12 August 2003 11:40, Jeff Newbern wrote:
> Hello everyone,
>
> Due to the scarcity of monad tutorials available (:^), I have
> written one of my own. I hope that this one is both more gentle
> a
31 matches
Mail list logo
