Thu, 30 Sep 1999 02:08:23 +1000, Fergus Henderson <[EMAIL PROTECTED]> pisze:
> > I only don't like the details about IOError. It's not extensible
> > and Dynamic is still not nice. I have no idea how to make it
> > better. Probably some general way of making extensible datatypes.
>
> Could you e
> Just before everyone starts writing MVC (model-view-controller)
> GUIs, you should be aware that there is a later development called
> MVP (model-view-presenter), which decouples the components
> even more.
>
> Main Dolphin site:
>
http://www.object-arts.com
Thanks for the link.
I found this b
I thank Fergus Henderson <[EMAIL PROTECTED]>
and Dave Tweed <[EMAIL PROTECTED]>
for the explanations on the Cryptarithm test, its C++ program.
Fergus Henderson writes
> But the comment about the ratio being smaller will probably not be,
> because the conditions when pass-by-value must be u
I am trying to get Malcolm Wallace's Xtract code to run with Hugs and have
noticed a few inconsistencies between whatever compiler he is using and
hugs...
1. Where `maybe` is exported
His compiler does not export `maybe` from the Maybe library but Hugs
does. The report says that Maybe should be
Fergus Henderson wrote:
[snip]
> So why limit expressiveness by providing only the former?
Why indeed? You are right. I hadn't realised that
a -> IO (Maybe a)
would still suffer from non-determinism.
(Because if you have
x = error "foo" + _|_
it may cause a return of Nothing or else no
Alastair Reid wrote:
> [discussion of Dynamic library, etc deleted]
>
> [...]
>
> If Haskell supported extensible datatypes, it would be easy to define a
> hierarchy of exception values. For example, the attached pseudocode
> creates a hierarchy like this:
>
> IOError
> Win32Error
>
Fergus Henderson wrote:
[snip]
> SML's exception mechanism essentially forces sequential execution,
> and (I think) causes problems for equational reasoning.
> Haskell's exception mechanism preserves referential transparency
> and gives the compiler more freedom to reorder and/or parallelize code.
[ Apologies that this message is not about Haskell,
but it is about interesting use of language! ]
Amazingly, Perec's book has been translated into English,
by Gilbert Adair, completely maintaining it's "e-less"
constraint! The title of the English translation is
"A Void" (the French title wou
Wed, 29 Sep 1999 11:43:06 +0200, George Russell <[EMAIL PROTECTED]> pisze:
> When that happens in my code it counts as a bug! Therefore error
> is appropriate. If you are in some larger Haskell universe calling
> component Haskell code it is unfortunate if a single error calls the
> entire univ
> "Fergus" == Fergus Henderson <[EMAIL PROTECTED]> writes:
Fergus> On 28-Sep-1999, Paul Hudak <[EMAIL PROTECTED]> wrote:
>> > Haskell's (&&) only models the logical AND when it is passed booleans.
>> > To say that _|_ is a Haskell Boolean, is to create another concept
>> > domain (Haskell Boo
Fergus Henderson wrote:
[many interesting things which are snipped]
> There are many common examples where exceptions arise for reasons other
> than I/O, for example integer overflow, division by zero, taking the
> square root of a negative number, head of an empty list, and so forth.
When that ha
>
>Havoc Pennington wrote:
>>
>> On Mon, 27 Sep 1999, Antony Courtney wrote:
>> >
>> > First, it is possible to write applications in Haskell using event loops
>> > and mutable state. Most of the simple toolkit bindings (such as
>> > TclHaskell, which is really a binding to Tk) do this.
>> >
>>
Josef Sveningsson wrote:
> On Mon, 27 Sep 1999, Havoc Pennington wrote:
>
> > The question is: how do you structure a GUI program?
>
> There is one paper I can recommend that tries to answer this question;
> "Structuring Graphical Paradigms in TkGofer". It can be found here:
>
> http://www.cs.
On 29 Sep 1999, Marcin 'Qrczak' Kowalczyk wrote:
> Wed, 29 Sep 1999 11:43:06 +0200, George Russell <[EMAIL PROTECTED]> pisze:
>
> > When that happens in my code it counts as a bug! Therefore error
> > is appropriate. If you are in some larger Haskell universe calling
> > component Haskell co
On Tue, 28 Sep 1999, S. Alexander Jacobson wrote:
> My simple point is that claims about the correctness or incorrectness of
> the behavior of a function are incoherent outside the function's domain;
> that, as an language implementation matter, it is handy to make _|_ a
> member of all types is
On 28-Sep-1999, Paul Hudak <[EMAIL PROTECTED]> wrote:
> > I don't think it is correct to say that the notion of _|_ invariably
> > creeps into the denotational semantics.
> > But perhaps I am misusing the term "denotational semantics".
> >
> > In languages such as Goedel and Mercury, the declarat
On 28-Sep-1999, Alastair Reid <[EMAIL PROTECTED]> wrote:
>
> > > > (b) allow throwing and catching of dynamically typed values,
> > > > e.g. using an interface like the Hugs/ghc Dynamic library
>
> [discussion of Dynamic library, etc deleted]
>
> [The following is a bit of a straw-man: it d
I've now got a .pdf (with decent fonts, I think) and some patches to
upgrade some of the ancient Latex I was using. I'll get a patched
version on the web later today (no technical changes - just slightly
nicer formatting). Thanks to all who helped ...
John
On 28-Sep-1999, Paul Hudak <[EMAIL PROTECTED]> wrote:
> > Haskell's (&&) only models the logical AND when it is passed booleans.
> > To say that _|_ is a Haskell Boolean, is to create another concept
> > domain (Haskell Boolean), which shares many properties with Logic
> > Boolean but is not ident
On 28-Sep-1999, Paul Hudak <[EMAIL PROTECTED]> wrote:
> There seems to be serious confusion here!
>
> True and False are the only "fully determined" members of Bool. But,
> even in imperative languages, it is possible for a boolean-typed
> expression to diverge, or possibly cause an error -- nei
On 28-Sep-1999, Alastair Reid <[EMAIL PROTECTED]> wrote:
>
> Fergus Henderson <[EMAIL PROTECTED]> replied:
> > What existing functions for testing IOErrors?
> > Apart from the Eq and Show classes, Haskell 98 doesn't define any, AFAIK.
>
> The IO library defines these functions.
> (http://haskell
On 28-Sep-1999, George Russell <[EMAIL PROTECTED]> wrote:
> I must be missing something. Isn't it blindlingly obvious that
> here SML's exception mechanism is streets ahead of Haskell's? Please,
> what am I missing? Is there some lurking type-unsafeness?
SML's exception mechanism essentially f
On 28-Sep-1999, Alex Ferguson <[EMAIL PROTECTED]> wrote:
>
> It would be interesting to investigate adding 'dynamic classes' to
> Haskell, but it introduces the issue of what type to give the resulting
> function: I think I'd want to clearly distinguish between a genuine
> (boundedly) polymorphi
On 28-Sep-1999, S.D.Mechveliani <[EMAIL PROTECTED]> wrote:
> Fergus Henderson <[EMAIL PROTECTED]> writes
> > On 28-Sep-1999, S.D.Mechveliani <[EMAIL PROTECTED]> wrote:
> >> And now the performance ratio shows * 16 *.
> >>
> >> I understand this so, that this particular task allows to set
> >> `
On 08-Sep-1999, Alastair Reid <[EMAIL PROTECTED]> wrote:
>
> I recently had occasion to write this function:
>
> -- do a, if that fails do b, if that fails, raise b's exception
> (?) :: IO a -> IO a -> IO a
> a ? b = a `catch` \_ -> b
>
> Simple enough, but if b fails, I don't really wan
On 28-Sep-1999, S.D.Mechveliani <[EMAIL PROTECTED]> wrote:
> D. Tweed <[EMAIL PROTECTED]> writes
> T> One small comment is that in your functions condition1 & condition2 I
> T> think most C++ programmers would say that you want to write
> T>
> T> int condition1 (const vector& x)
> T>
> T> sinc
On 28-Sep-1999, Andreas C. Doering <[EMAIL PROTECTED]> wrote:
> > The trickier part is putting different types into a heterogenous
> > collection, and then manipulating according to their _individual_ types.
>
> If we are already at this point, a naive question:
>
> Assume we add the type of all
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