| On that note, I've been finding GHC's type suggestions often worse
| than useless, and wish it wouldn't even bother to try -- even more
| confusing for new users to have the compiler suggest pointless things
| like declaring an instance of Num String or whatever. I'd prefer it
| if it could just
On Wed, 5 Sep 2007, ok wrote:
On 5 Sep 2007, at 6:16 pm, Henning Thielemann wrote:
I think it is very sensible to define the generalized function in terms of
the specific one, not vice versa.
The specific point at issue is that I would rather use ++ than
`mplus`. In every case where both a
David Benbennick wrote:
You mean (++) = mplus. I've wondered that too. Similarly, one should
define map = fmap. And a lot of standard list functions can be
generalized to MonadPlus, for example you can define
filter :: (MonadPlus m) => (a -> Bool) -> m a -> m a
Somehow this filter fails my
ok wrote:
On 5 Sep 2007, at 6:16 pm, Henning Thielemann wrote:
I think it is very sensible to define the generalized function in
terms of the specific one, not vice versa.
The specific point at issue is that I would rather use ++ than
`mplus`. In every case where both are defined, they agree,
On Wed, 2007-09-05 at 08:19 +0100, Simon Peyton-Jones wrote:
> | confusing for new users to have the compiler suggest pointless things
> | like declaring an instance of Num String or whatever.
This also gets my vote for the
"Error-message-most-likely-to-be-unhelpful"-award. IME, this often
aris
On Wed, 2007-09-05 at 13:02 +1000, Donald Bruce Stewart wrote:
> The xmonad dev team is pleased to announce the 0.3 release of xmonad.
I just wanted to congratulate the team, and say that xmonad is, along
with darcs, my favorite "mainstream" Haskell program. I used to spend
days experimenting w
| > when you come across a case where GHC produces an
| > unhelpful message, send it in, along with the program
| > that produced it,
|
| Contents of test/error.hs:
| f x s = x + show s
|
| Error message from GHCi:
| test/error.hs:2:8:
| No instance for (Num
IMHO error reporting should be done in a hierarchical manner, so that
you get a very brief description first, followed by many possible hints
for fixing it, and each hint could have subhints etc... Now to make this
easy to read, it should be integrated into some IDE of course, otherwise
it woul
Looks really nice, but if I understand it correctly it is specific for
X, so does not work on Windows?
If so, would it be possible to integrate this into GTK2HS so it works as
a docking manager inside an application?
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Sterling Clover <[EMAIL PROTECTED]> writes:
> of course you could rewrite this in a while loop too
> although you'd have to use an assignment, but at least
> still not one with a silly "done" variable.
People seem to have overlooked the bit of Algol68 I posted,
so I'll repeat it
While If E
> WARNING: Learning Haskell is dangerous to your health!
:-) I liked that so much I made a hazard image to go with it.
http://malde.org/~ketil/Hazard_lambda.svg
-k
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On Wed, 2007-09-05 at 09:56 +0100, Simon Peyton-Jones wrote:
> Is your suggestion specific to String?
No.
> then I really might have intended to use Complex as a Num type
IME this is much rarer, and I think if a newbie is told that Complex is
not (but needs to be) and instance of Num, it is re
Ketil Malde wrote:
WARNING: Learning Haskell is dangerous to your health!
:-) I liked that so much I made a hazard image to go with it.
http://malde.org/~ketil/Hazard_lambda.svg
Cool! Can we have a license to reuse that image? (I want it on a T-shirt)
Cheers,
Simon
___
On Sep 5, 2007, at 6:47 , Ketil Malde wrote:
On Wed, 2007-09-05 at 09:56 +0100, Simon Peyton-Jones wrote:
Good point. Not so easy for multi-parameter type classes! E.g. No
instance for (Bar String Int). So we could have
String is not an instance of class Foo -- single param
On Wed, 2007-09-05 at 12:06 +0100, Simon Marlow wrote:
> Ketil Malde wrote:
> >> WARNING: Learning Haskell is dangerous to your health!
> >
> > :-) I liked that so much I made a hazard image to go with it.
> >
> > http://malde.org/~ketil/Hazard_lambda.svg
>
> Cool! Can we have a license to reus
Ketil Malde wrote:
String is not an instance of class Foo -- single param
No instance for (Bar String Int)-- multi-param
If you quote things, you can also consider:
'String Int' is not an instance of class 'Bar'.
Downside is that 'String Int' by it
Simon Marlow writes:
Ketil Malde wrote:
WARNING: Learning Haskell is dangerous to your health!
:-) I liked that so much I made a hazard image to go with it.
http://malde.org/~ketil/Hazard_lambda.svg
Cool! Can we have a license to reuse that image? (I want it on a T-shirt)
People, are yo
On 9/5/07, Ketil Malde <[EMAIL PROTECTED]> wrote:
> On Wed, 2007-09-05 at 08:19 +0100, Simon Peyton-Jones wrote:
> Error message from GHCi:
> test/error.hs:2:8:
> No instance for (Num String)
> arising from use of `+' at test/error.hs:2:8-17
> Possible fix: add an inst
Hello Simon,
Wednesday, September 5, 2007, 11:19:28 AM, you wrote:
> when you come across a case where GHC produces an
> unhelpful message, send it in, along with the program
> that produced it,
i have put such tickets about year ago :) basically, it was about
just chang
Hello Simon,
Wednesday, September 5, 2007, 12:56:18 PM, you wrote:
> String is not an instance of class Foo -- single param
> No instance for (Bar String Int)-- multi-param
> Would that be better (single-param case is easier), or worse (inconsistent)?
easier - m
I agree actually. That picture, while very cool, won't help Haskell
marketing one bit. :)
Lisp's "made with alien technology" is much more inviting:
http://www.lisperati.com/logo.html . I wish we could use it!
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I'd prefer something slightly more specific, such as instead of
No instance for (Num String)
arising from use of `+' at test/error.hs:2:8-17
Possible fix: add an instance declaration for (Num String)
In the expression: x + (show s)
In the definition of `f
Bulat Ziganshin wrote:
Hello Simon,
Wednesday, September 5, 2007, 11:19:28 AM, you wrote:
when you come across a case where GHC produces an
unhelpful message, send it in, along with the program
that produced it,
i have put such tickets about year ago :) basically, it
I want to have a data structure like Data.ByteString.Lazy, that is
block-wise lazy, but polymorphic. I could use a lazy list of unboxed
arrays (UArray) but the documentation says, that the element types are
restricted. But I will need (strict) pairs of Double and the like as
elements. It see
On Wed, 2007-09-05 at 19:50 +0200, Twan van Laarhoven wrote:
> Bulat Ziganshin wrote:
> > Hello Simon,
> >
> > Wednesday, September 5, 2007, 11:19:28 AM, you wrote:
> >
> >
> >>when you come across a case where GHC produces an
> >>unhelpful message, send it in, along with the pro
Henning Thielemann wrote:
I thought it must be possible to define an unboxed array type with
Storable elements.
Yes, this just hasn't been done. There would be a few potentially
tricky corners, of course; Storable instances are not required to be
fixed in size, though all the precanned ins
On Wed, 5 Sep 2007, Bryan O'Sullivan wrote:
Henning Thielemann wrote:
I thought it must be possible to define an unboxed array type with
Storable elements.
Yes, this just hasn't been done. There would be a few potentially tricky
corners, of course; Storable instances are not required to
Can someone explain me, why there are arrays with mutable but boxed
elements? I thought that boxing is only needed for lazy evaluation.
However if I access an element of an array that is the result of a
sequence of in-place updates, all updates must be executed in order to get
the final value
On Wed, Sep 05, 2007 at 07:54:34PM +0200, Henning Thielemann wrote:
>
> I want to have a data structure like Data.ByteString.Lazy, that is
> block-wise lazy, but polymorphic. I could use a lazy list of unboxed arrays
> (UArray) but the documentation says, that the element types are restricted.
I'm not sure I understand your point : why would access to a specific
element of the array make all the other elements evaluate (or even
this specific element as long as you don't deconstruct it).
Besides you misunderstood the "box" concept, indeed only primitive
values that fits in 32 bits can be
2007/9/5, Chaddaï Fouché <[EMAIL PROTECTED]>:
> indeed only primitive values that fits in 32 bits can be unboxed
Note that there are some cases which could make you doubt that, like
the UArray Bool (bool isn't a primitive type), but that's because
UArray Bool don't really use unboxed bool, it's a
[EMAIL PROTECTED] wrote:
People, are you crazy, with my deepest respect and friendliness...
You want to frighten newbies? it seems that they have already a good dose
of allergy...
I am way over 30 years old, and my age would have me agree with you.
But I have also looked at the culture of peop
On Wed, 2007-09-05 at 20:37 +0200, Henning Thielemann wrote:
> Can someone explain me, why there are arrays with mutable but boxed
> elements? I thought that boxing is only needed for lazy evaluation.
> However if I access an element of an array that is the result of a
> sequence of in-place upd
[bcc haskell, cc haskell-cafe]
On 9/5/07, Tomi Owens <[EMAIL PROTECTED]> wrote:
>
> Hi there. I'm a teacher of Maths and am working my way through the Euler
> Project problems for fun. I have mostly been using Basic, but have read up
> about Haskell and think it looks like a sensible way to solve
I think you want something like this
{-# OPTIONS -fglasgow-exts #-}
f :: (Integer, Float) -> Integer
f (a,b) = a * floor (10/b)
lst :: [(Integer, Integer)]
lst = [(a ^ 2 + b ^ 2, a) | a <- [1..4], b <- [1..4], a^2 + b^2 < 20, b <=
a]
lst3 = map (f) ( map ( intTupToFloatTup ) lst )
intTu
G'day all.
Slight nit...
Quoting ok <[EMAIL PROTECTED]>:
I've been thinking about making a data type an instance of MonadPlus.
From the Haddock documentation at haskell.org, I see that any such
instance should satisfy
mzero `mplus` x = x
x `mplus` mzero = x
mzero >>= f
2007/9/5, Peter Verswyvelen <[EMAIL PROTECTED]>:
> Looks really nice, but if I understand it correctly it is specific for
> X, so does not work on Windows?
This kind of programs is impossible in Windows. Of cause you can use X
server for Windows and xmonad as window manager with X server.
> If so,
Instead of just adapting the compiler to give better errors, it would
really help if a unique identifier was assigned to each error/warning,
and if a WIKI and help file existed that describes the errors in detail.
Maybe this is already the case, but after a quick search I failed to
find such a
Paul Johnson wrote:
> For software developers who need to produce highly reliable software at
> minimum cost, Haskell is a pure functional programming language that
> reduces line count by 75% through reusable higher order functions and
> detects latent defects with its powerful static type system.
On Wed, 2007-09-05 at 20:37 +0200, Henning Thielemann wrote:
> Can someone explain me, why there are arrays with mutable but boxed
> elements?
I, on the other hand, have always wondered why the strict arrays are
called "unboxed", rather than, well, "strict"? Strictness seems to be
their observab
On Wed, 2007-09-05 at 09:54 -0700, Simon Michael wrote:
> I agree actually. That picture, while very cool, won't help Haskell
> marketing one bit. :)
Avoid success at all costs, remember?
> Lisp's "made with alien technology" is much more inviting:
> http://www.lisperati.com/logo.html .
Tru
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