To me, perhaps naively, IncoherentInstances is way more scary than
OverlappingInstances.
What behavior do these new pragmas have? In particular, will it be an error if
there is no single most specific instance? And can the user decide whether it is
an error?
Twan
On 29/07/14 11:11, Simon
Why does every section have a title=1.2.3 foo on the outer div? In Firefox
this shows up as a useless tooltip when moving the mouse over the text.
On 11/09/13 13:31, Obscaenvs wrote:
At [1] you can find links to the GHC documentation that I use myself,
since the official version is a bit too
On 13/08/13 17:38, Andreas Abel wrote:
Indeed, I wished the 0-ary case would be more alike to the unary and binary
case, cf.
return f0
f1 $ a1
f2 $ a1 * a2
You could always write the above as
pure f0
pure f1 * a1
pure f2 * a1 * a2
Twan
The standard array types, such as Array (n,n) (Maybe w) will be implemented as
a dense array. If you want to use a sparse matrix, you will explicitly have to
ask for it. For instance by using something like IntMap (IntMap w) or Map
(n,n) w or Array n (IntMap w). Each of these representations is
On 02/07/13 10:57, Simon Peyton-Jones wrote:
Here is Plan A: use fundep (or type function)
class Has r f t | r f - t where
getFld :: r - t
instance Has (R a) “foo” (a - a) where ..
instance Has S “bar” (forall b. b - b) where ...
Lacking (as we still do) impredicative
On 25/02/13 07:06, Michael Snoyman wrote:
Quite a while back, Simon Hengel and I put together a proposal[1] for a new
feature in GHC. The basic idea is pretty simple: provide a new pragma that could
be used like so:
error :: String - a
errorLoc :: IO Location - String - a
{-#
On 25/02/13 13:41, Michael Snoyman wrote:
At that point, we've now made two changes to REWRITE rules:
1. They can takes a new ALWAYS parameters.
2. There's a new, special identifier currentLocation available.
What would be the advantage is of that approach versus introducing a single new
On 20/02/13 08:13, Jan Stolarek wrote:
Dnia wtorek, 19 lutego 2013, Gwern Branwen napisał:
On Tue, Feb 19, 2013 at 5:36 PM, Jan Stolarek jan.stola...@p.lodz.pl wrote:
- remove unlambda, brainfuck and show from the repo. They are on hackage,
no need to keep them here - these packages aren't
On 18/02/13 13:41, Amy de Buitléir wrote:
I'm happy to announce a new major release of the grid package:
http://hackage.haskell.org/package/grid
https://github.com/mhwombat/grid/wiki (wiki)
After taking a peek at the documentation: have you considered removing the size
function
On 31/01/13 09:16, Ketil Malde wrote:
*MY* proposal is that:
0. Hackage sends an email to the previous uploader whenever a new
version of a package is uploaded by somebody else.
At least that way, I would be notified if it happened to my packages,
and I would be able to check up on the
On 24/10/12 12:08, Jon Fairbairn wrote:
Is there a convenient way of handling a data structure with lots
of fields of different types that may or may not be filled in?
Not sure about convenience, but here is a type safe solution with O(log n)
lookups and updates. The idea is to define a
On 16/08/12 14:07, Chris Smith wrote:
As a package author, when I
release a new version, I know perfectly well what incompatible changes
I have made to it... and those might include, for example:
1. New modules, exports or instances... low risk
2. Changes to less frequently used, advanced, or
On 15/08/12 17:01, José Lopes wrote:
someFn docs =
return concat `ap` (sequence $ intersperse (return \n) (map loop docs))
First of all, return x `ap` y = x `fmap` y or x $ y. fmap (or its infix
synonym ($)) is the answer here, you could write:
someFn docs = concat . intersperse \n $
On 14/08/12 13:46, Ketil Malde wrote:
AntC anthony_clay...@clear.net.nz writes:
I agree. I don't declare operators very often, and when I do I always struggle
to remember which way round the precedence numbers go.
[...]
(Anything else we can bikeshed about while we're at it?)
infixl
On 26/07/12 12:40, Евгений Пермяков wrote:
class Applicative f = Actuative f where
-- | select computation conditionally . Side effects of only one two
alternative take place
select :: f (Either a b) -- ^ selector
- f (a - c) -- ^ first alternative
-
On 26/07/12 13:58, Евгений Пермяков wrote:
As you can see, if I use select definition with Control.Applicative.*, I'll
execute both l and r and the only choice will be, what result to drop. Both l
and r, however, will be executed, and their side effects will take place. With
select from my code
On 2012-07-25 22:22, Евгений Пермяков wrote:
Let assume, that some computation takes argument and produces value Either a b.
This computation may be represented in for different forms
computePure :: a - Either b c
computeMonad :: a - m (Either b c)
computeApplicative :: app a - app
On 2012-07-24 10:10, Christian Sternagel wrote:
Dear all,
with respect to formal verification of Haskell code I was wondering whether (==)
of the Eq class is intended to be commutative (for many classes such
requirements are informally stated in their description, since Eq does not have
such a
On 24/07/12 13:32, Frank Recker wrote:
I agree, that (==) should be symmetric. However, it is easy to write
Eq-instance, which violates this law:
It is impossible to specify laws such as symmetry in Haskell, which is why they
are usually stated in the documentation. However, this style of
On 24/07/12 14:39, Jonas Almström Duregård wrote:
Hi,
I suppose you need to define what commutativity means in the presence
of undefined values. For instance if error 0 is different from error
1 then you do not have commutativity. Also nontermination needs to
be considered, for instance (fix $
On 24/07/12 14:44, timothyho...@seznam.cz wrote:
There's always this, for ALL types a :( So even where you would think that the
documentation can claim that a given Eq instance follows the law of
commutativity, it really cannot.
Once you invoke unsafePerformIO, you can break the type system,
On 2012-07-12 23:48, Bulat Ziganshin wrote:
another interesting feature may be ruby-style matching defined by
execution of special function `match` instead of pattern matching:
switch var of
1+1 - print var==2
[5..10] - print var in [5..10]
(20) - print var20
where (var `match`
On 09/07/12 14:44, Simon Marlow wrote:
I now think '\' is too quiet to introduce a new layout context. The pressing
need is really for a combination of '\' and 'case', that is single-argument so
that we don't have to write parentheses. I think '\case' does the job
perfectly. If you want a
On 05/07/12 17:22, wagne...@seas.upenn.edu wrote:
Well, for what it's worth, my vote goes for a multi-argument \case. I find the
comment on the wiki page about mistyping \case Just x instead of \case (Just
x) a lot a bit disingenuous, since you already need these parens with today's
lambda.
On 2012-07-05 23:04, Edward Kmett wrote:
A similar generalization can be applied to the expression between case and of
to permit a , separated list of expressions so this becomes applicable to the
usual case construct. A naked unparenthesized , is illegal there currently as
well. That would
On 05/07/12 17:18, rickmurphy wrote:
Hi All:
I've been working through some details in these papers [1], [2] and
noticed a language pragma configuration that I hope you can confirm.
When using explicit foralls in a data constructor, it appears that GHC
7.4.2 requires Rank2Types in the Language
On 24/05/12 14:14, AntC wrote:
Simon Peyton-Jonessimonpjat microsoft.com writes:
[from 7 Jul 2010. I've woken up this thread at Oleg's instigation
http://www.haskell.org/pipermail/haskell-prime/2011-July/003491.html ]
I'm not going to talk about Fundeps. This is about introducing
On 04/05/12 09:08, Magicloud Magiclouds wrote:
Hi,
Assuming this:
run :: Monad IO a - IO a
data Test = Test { f }
Here I'd like to set f to run, like Test run. Then what is the type of f?
The confusing (me) part is that, the argument pass to f is not fixed
on return type, like f1 ::
On 10/04/12 09:55, Arnaud Bailly wrote:
Hello,
I am manipulating labeled multiway trees, some kind of lightweight
XML notation. One thing I would like to be able to do is manipulating
a tree as a list of (Path, Value). Generating such a list is easy but
I am a little bit surprised to find it
On 09/04/12 23:49, Paolo Capriotti wrote:
I'm pleased to announce the release of version 0.1.0 of pipes-core, a
library for efficient, safe and compositional IO, similar in scope to
iteratee and conduits.
http://hackage.haskell.org/package/pipes-core
I have some issues with the function
On 2012-04-07 23:35, Myles C. Maxfield wrote:
CC: Maintainers of STMonadTrans, Vector, and JuicyPixels
Hello,
I am writing a Haskell Attoparsec parser which will modify 2-d arrays
of small values (Word8, Int8, etc.).
My first idea was to simply parse all the deltas, and later apply them
to the
On 16/03/12 10:45, Rouan van Dalen wrote:
Hi everyone.
I was wondering if I can make assumptions about the evaluation order of
the following code:
isTrue :: Int - IO Bool
isTrue val = pure (||) * boolTest1 val * boolTest2 val
{- boolTest1 is an inexpensive, quick check -}
boolTest1 :: Int -
On 11/03/12 23:41, Chris Smith wrote:
On Sun, Mar 11, 2012 at 2:33 PM, Twan van Laarhoventwa...@gmail.com wrote:
I think you should instead move unwaits in and out of the composition on the
left side:
unawait x (p1+ p2) === (unawait x p1)+ p2
This makes idP a left-identity for (+),
On 2012-03-11 14:09, Paolo Capriotti wrote:
The Category law would be broken, though:
unawait x id == yield x !== unawait x
How did you get this equation? It's not even well-typed:
unawait :: a - Pipe a b m ()
yield :: b - Pipe a b m ()
I would expect that
(id unawait x) await
On 2012-03-11 14:46, Paolo Capriotti wrote:
On Sun, Mar 11, 2012 at 1:25 PM, Twan van Laarhoventwa...@gmail.com wrote:
I would expect that
(id unawait x) await !== unawait x await === return x
There are several type errors in this equation, so I'm not exactly
sure what you mean.
On 2012-03-11 17:30, Mario Blažević wrote:
It's difficult to say without having the implementation of both unawait and all
the combinators in one package. I'll assume the following equations hold:
unawait x await = return x
unawait x yield y = yield y unawait x
(p1 unawait x) p2 = (p1 p2)
On 2012-03-10 11:16, Paolo Capriotti wrote:
Another issue is how to deal with unconsumed input. For that, there is
a ChunkPipe type (in pipes-extra) with a specialized monad instance
that threads unconsumed input along. You can see an example of
ChunkPipe in action in this prototype http server
On 2012-03-11 00:09, Mario Blažević wrote:
On 12-03-10 05:19 PM, Twan van Laarhoven wrote:
-- | Pass some unconsumed input back upstream.
-- The next @await@ will return this input without blocking.
unawait :: Monad m = a - Pipe a b m ()
The function may be called unawait, but there's nothing
On 2012-03-09 02:13, Johan Tibell wrote:
Hi,
I just ran across some code that calls unsafeThawArray#, writeArray#,
and unsafeFreezeArray#, in that order. How unsafe is that?
Quick follow up question:
Are unsafeThawArray# and unsafeFreezeArray# guaranteed to not make a copy? I.e.
are these
On 03/03/12 01:40, Johan Tibell wrote:
Hi all,
These ideas are still in very early stages. I present them here in hope
of starting a discussion. (We discussed this quite a bit at last year's
ICFP, I hope this slightly different take on the problem might lead to
new ideas.)
I think the next big
On 25/01/12 16:21, Thijs Alkemade wrote:
Hello!
...
Examples:
*Main :t [__, ()]
tcRnExpr2: [(interactive:1:2-3, ())]
[__, ()] :: [()]
*Main :t map __ __
tcRnExpr2: [(interactive:1:5-6, a0 - b), (interactive:1:8-9, [a0])]
map __ __ :: [b]
You can do something similar right now with
On 2012-01-20 23:44, Gwern Branwen wrote:
On Fri, Jan 20, 2012 at 1:57 PM, Twan van Laarhoventwa...@gmail.com wrote:
Here is some example code (untested):
Well, you're right that it doesn't work. I tried to fix the crucial
function, 'atLeastThisManyDescendants', but it's missing something
On 2012-01-22 00:39, Pierre Penninckx wrote:
So here is what I want to achieve:
I'd like a program that calculates the time needed for water to flow out of a
circuit made out of tube.
The rules are :
- There are multiple sources of water and only one exit.
- The water can only take one path from
On 20/01/12 16:31, Mikhail Arefiev wrote:
Is there a reason why there is no instance of (Enum a) = IArray
UArray a (other than that it will require OverlappingInstances and/or
IncoherentInstances if e. g. UArray of Bools is used in the same
code)?
...
Does having such thing make any
On 20/01/12 18:45, Gwern Branwen wrote:
Recently I wanted to sort through a large folder of varied files and
figure out what is a 'natural' folder to split out, where natural
means something like4 files with the same prefix.
My idea for an algorithm would be: build a trie for the input
On 06/12/11 18:48, wren ng thornton wrote:
So, I have an optimization/internals question. Does the GHC API have any
hooks for being able to revert a CAF to the original expression, thus
discarding the previously computed result?
...
I could hack something together based on unsafePerformIO and
On 23/11/11 23:02, Tom Murphy wrote:
Is there a reason that the Haskell 2010 report is in a subdirectory of
haskell.org/onlinereport http://haskell.org/onlinereport (which
currently points to the Haskell98 standard)?
http://www.haskell.org/onlinereport/ -- Haskell98
On 18/11/11 06:44, Johan Tibell wrote:
On Thu, Nov 17, 2011 at 9:21 PM, Johan Tibelljohan.tib...@gmail.com wrote:
I'm not entirely happy with this formulation. I'm looking for
something that's clear (i.e. precise and concise, without leaving out
important information), assuming that the reader
On 18/11/11 09:18, Ivan Lazar Miljenovic wrote:
On 18 November 2011 19:06, Roman Cheplyakar...@ro-che.info wrote:
Maybe have a switch that enables markdown and disables markup-related
features of haddock (everything except linking to identifiers/modules, I
believe), so that we don't affect
On 03/11/11 11:16, Bas van Dijk wrote:
...
instance (Constructor c, GFromJSON a, ConsFromJSON a) = GFromSum (C1 c a) where
gParseSum (key, value)
| key == pack (conName (undefined :: t c a p)) =
gParseJSON value
| otherwise = notFound $ unpack key
{-#
On 24/09/11 05:21, Evan Laforge wrote:
hex2 = (+)$ ((*16)$ higit)* higit
higit = subtract (fromEnum '0')$ satisfy isHexDigit
color = Color$ hex2* hex2* hex2
How is subtract (fromEnum '0') supposed to convert a hex digit to an
Int or Word8? I think you need digitToInt (or an equivalent
On 2011-09-21 22:06, Brent Yorgey wrote:
On Tue, Sep 20, 2011 at 10:31:58PM -0400, Richard Cobbe wrote:
numVarRefs :: Term - Integer
numVarRefs (view - Var _) = 1
numVarRefs (view - App rator rand) = numVarRefs rator + numVarRefs rand
numVarRefs (view - Lam _ body) =
On 2011-06-27 13:51, Steffen Schuldenzucker wrote:
Could you specify what exactly the function is supposed to do? I am
pretty sure that a function like
seqPeriod :: (Eq a) = [a] - Maybe Integer -- Nothing iff non-periodic
cannot be written.
What about sequences that can be specified in terms
On 02/05/11 13:10, John Sneer wrote:
Simply: I would like to have direct access into several places
in a very long list.
Maybe you could use a zipper. Or just maintain the list split into
chunks. So l' = [stuffBefore,hi,stuffAfter].
Or if you want to be able to use each element of hi as a
On 08/04/11 11:54, Heinrich Apfelmus wrote:
Hello,
I'm writing a small Haskell library for functional reactive programming.
The core of the library consists of two data types and several
primitives. However, I have programmed this core *twice*: once as a
*model* that displays the intended
Max Bolingbroke wrote:
I don't actually know what the right name for this data type is, I
just invented it and it seems to work:
-- () :: forall a b. t a b - (forall c. t b c - t a c)
newtype Wotsit t a b = Wotsit { runWotsit :: forall c. t b c - t a c }
There is of course no reason to
Casey Hawthorne wrote:
Is there good place to post Haskell alorithms/data structures that
follow Steven Skiena's book on algorithm design and also Haskell code
snippets that follow some of Knuth's books?
These code snippets don't seem to fit with Hackage.
You could make some pages for them on
Ivan Lazar Miljenovic wrote:
I've been thinking of doing something similar for a year or so now, but
there's one big problem that I can think of: how to deal with functions
that don't have an explicit type signature in the source. My
understanding is that to derive these signatures at checking
Christopher Done wrote:
That's true, it's a nice idea but in practice it's hard to know where
to focus. I've gone with a left nav. I've built up the HTML which is
cross-browser (ie6/7/8/opera/firefox/safari/chrome compat), still need
to add some bits but I can tomorrow import it into a wikimedia
Bas van Dijk wrote:
...
However now comes the problem I would like to talk about. What if I
want to use modifyMVar_ as part of a bigger atomic transaction. As in:
block $ do ...
modifyMVar_ m f
...
From a quick glanse at this code it looks like asynchronous exceptions
Max Bolingbroke wrote:
2010/2/2 Isaac Dupree m...@isaac.cedarswampstudios.org:
I'm concerned in both your proposals, that single-letter names like t and
d are common function parameters, thus possibly producing
- shadowing warnings for all such functions in modules that happen to use TH
-
Hans Aberg wrote:
For example, in Map String Integer (sparse representation of monomials)
compute the minimum value of all associative pairs with the same key
(the gcd); if only one key is present, the absent should be treated as
having value 0. So
unionWith min xs ys
will not work, because
John Millikin wrote:
Earlier today I uploaded the capped-list package; I didn't think there
would be any interest, since it's a relatively trivial data structure,
but already there's been three emails and an IRC convo about it.
Since uploading, there's been a big problem pointed out to me
John Van Enk wrote:
Hi Heinrich,
I think I like Ring more than Necklace or Tom's suggestion of Circular.
I chose Ring simply because that's what I was searching for when I
wanted the data structure. The package will be named data-ring, so that
should hopefully be enough to clue in the user
Alberto G. Corona wrote:
Hi haskell cafe:
concerning Stable Names
The IO in makeStableName suggest more side effects than makeStableName
really do. But still the call isn't pure.
For calls such are makeStableName that gives a different result the
FIRST time they are called but return the
David Sankel wrote:
After reading several recent papers I came to the understanding that
there isn't consensus on the name of Applicative Functors. Several
prefer to call them idioms:
'Idiom' was the name McBride originally chose, but he and Paterson
now favour the less evocative term
Nicolas Pouillard wrote:
The TDNR proposal really tries to do two separate things:
1. Record syntax for function application.
The proposal is to tread x.f or a variation thereof the same as (f x)
It is more like (ModuleToGuess.f x) than (f x).
My point is that desugaring x.f to (f
Levi Greenspan wrote:
What's the status of the TDNR proposal [1]? Personally I think it is a
very good idea and I'd like to see it in Haskell'/GHC rather sooner
than later. Working around the limitations of the current record
system is one of my biggest pain points in Haskell and TDNR would be a
Sjoerd Visscher wrote:
I believe this does what you want:
code
The attached code should be more efficient, since it doesn't use integer
indices.
Note that this is just a 'level' monad: the list is stratified into levels, when
combining two levels, the level of the result is the sum of the
John Meacham wrote:
On Mon, Jul 27, 2009 at 04:41:37PM -0400, John Dorsey wrote:
I'm assuming that name resolution is currently independent of type
inference, and will happen before type inference. With the proposal this is
no longer true, and in general some partial type inference will have
Jon Fairbairn wrote:
Warnings are the wrong answer to this problem. In fact,
they're rarely the right answer to any problem. Tabs in
sourcecode can have bad effects, and Haskell is a language
that attempts to reject bad effects as far as possible. Nor
can I see any argument in favour of
Hello Ghc people,
I have been working on adding support for derive Functor to ghc. I have a
patch that mostly works, but there are some problems:
1. Ghc reports the correct instance when I use -ddump-deriv:, but that instance
is not subsequenctly used. Instead I get a warning like:
Mauricio wrote:
Do you think 'read' (actually,
'readsPrec'?) could be made to also
read the international convention
(ie., read 1,5 would also work
besides read 1.5)? I'm happy to
finaly use a language where I can
use words of my language to name
variables, so I wonder if we could
also make that
Ronald Guida wrote:
I have read that Monad is stronger than Idiom because Monad lets me
use the results of a computation to choose between the side effects of
alternative future computations, while Idiom does not have this
feature. Arrow does not have this feature either.
ArrowChoice has the
sam lee wrote:
Hi.
I want to compose two monads to build another monad where
computations of the two monads can be used inside.
I have:
- MonadTypeInfer : interface (class) for TypeInfer monad
- TypeInfer : a monad that has Map String Type (association of names and types)
- TypeInferT :
Simon Peyton-Jones wrote:
Is this the most up-to-date description of the proposal?
http://repetae.net/recent/out/classalias.html
Has anyone looked at my (confusingly named and horribly written) variant?
http://haskell.org/haskellwiki/Superclass_defaults
My idea is to split
Cale Gibbard wrote:
Hello,
In keeping with my small but seemingly extremely controversial
suggestions for changes to the Prelude, here's a suggestion which I
think is elegant and worth considering for the Haskell' Prelude:
Rename fmap to map (like it was in Haskell 1.4), and define (.) as a
Hello,
I have just uploaded version 0.1 of the multiset library to hackage. This
package provides Data.MultiSet and Data.IntMultiSet modules. A multiset or bag
is like a set, but it can contain multiple copies of the same element.
The library is already pretty much finished, maybe I should
I am having some problems with the latest builds of GHC on windows. For some
reason ghc has decided to use backslashes in filenames. This leads to
problems when building the stage libraries and the stage 2 compiler. I run
the scripts from a mingw bash shell.
The following problems occur:
-
Twan van Laarhoven wrote:
I am having some problems with the latest builds of GHC on windows. For
some reason ghc has decided to use backslashes in filenames. This leads
to problems when building the stage libraries and the stage 2 compiler.
I run the scripts from a mingw bash shell.
After
Hello GHC people,
I was trying my hand at some GHC hacking, and I couldn't help but notice
that much of the code looks (IMHO) horrible. There are some things that look
as if they haven't been touched since the Haskell 1.3 days. The most
striking is the use of `thenXX` instead of do notation.
Isaac Dupree wrote:
Unfortunately, I get puzzling type errors if I annotate either one of
them with their type (e.g.
(Applicative f) = f (a - b) - f a - f (Int, b)
) in an expression. The very answer doesn't seem to typecheck.
:t \f x - fmap ((,) (0::Int)) (f * x) :: (Applicative f) = f (a1
Robin Green wrote:
I am proving various statements relating to applicative functors, using
the Coq proof assistant (I am considering only Coq terms, which always
terminate so you don't have to worry about _|_). However, I'm not sure
how to go about proving a certain conjecture, which,
alpheccar wrote:
Can someone confirm me that:
type TA = A :+: B
type TB = C :+: D
type T = TA :+: TB
This is
type T = (A :+: B) :+: (C :+: D)
is not equivalent to
type T = A :+: B :+: C :+: D
is
type T = A :+: (B :+: (C :+: D))
So these types are indeed not the same.
Twan
Ronald Guida wrote:
I'm playing around with smart constructors, and I have encountered a
weird puzzle.
My goal is to do vector arithmetic. I'm using smart constructors so
that I can store a vector as a list and use the type system to
staticly enforce the length of a vector.
So my first step
Jules Bean wrote:
Thomas Hartman wrote:
I found
http://haskell.cs.yale.edu/haskell-report/List.html
had many useful one off type list functions such as subsequences
and permutations which are nowhere to be found in hoogle, Data.List,
or the haskell hierarchical libs
Weird.
It's
Simon Peyton-Jones wrote:
Concerning (b) here's a suggestion. As now, require that every instance
requires an instance declaration. So, in the main example of
http://haskell.org/haskellwiki/Class_system_extension_proposal, for a new data
type T you'd write
instance Monad T where
Simon Peyton-Jones wrote:
Concerning (b) here's a suggestion. As now, require that every instance
requires an instance declaration. So, in the main example of
http://haskell.org/haskellwiki/Class_system_extension_proposal, for a new data
type T you'd write
instance Monad T where
Neil Mitchell wrote:
Hi
Under Hugs and Yhc, showing a Ratio 1%2 gives 1 % 2. Under GHC
showing 1%2 gives 1%2. Does the standard say anything about this? Is
someone wrong?
Yes, ghc is wrong here, the Haskell 98 report [1] specifies:
instance (Integral a) = Show (Ratio a) where
Hello,
I noticed there is a difference in generalized newtype deriving between
6.6 and 6.8. In GHC 6.4.1 the following:
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
import Control.Monad.Error
newtype MyMonad m a = MyMonad (m a)
deriving (Monad, MonadError String)
correctly gives a
Andrew Coppin wrote:
I'm writing some code where I take an expression tree and transform it
into another equivilent one.
Now it's moderately easy to write the code that does the transformation.
But what I *really* want is to print out the transformation *sequence*.
This appears to be much
Lots of people wrote:
I want a UTF-8 bikeshed!
No, I want a UTF-16 bikeshed!
What the heck does it matter what encoding the library uses internally?
I expect the interface to be something like (from my own CompactString
library):
fromByteString :: Encoding - ByteString - UnicodeString
Johan Tibell wrote:
Dear haskell-cafe,
I would like to propose a new, ByteString like, Unicode string library
which can be used where both efficiency (currently offered by
ByteString) and i18n support (currently offered by vanilla Strings)
are needed. I wrote a skeleton draft today but I'm a
PR Stanley wrote:
Hi
or = foldl (||) False
and = foldl () True
I can understand the rationale for the accumulator value - True []
where [] = True and True || [] where [] = False
Other than the practical convenience is there a reason for having the
empty list in and and or equating to True and
The bang pattern proposal [1] still allows (!) to be used as an
operator. I think there should be no difference in this regard between !
and ~, since they are used in exactly the same location.
In my opinion the best thing would be to allow (~) and (@) as operators.
With the same restriction
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
Stefan O'Rear wrote:
On Wed, Aug 22, 2007 at 06:36:15PM +0100, Neil Mitchell wrote:
Hi
If Num obeys ring axioms, fromInteger is a perfectly fine
ring-homomorphism. (It's also the first or second homomorphism taught.)
Does Int obey these axioms? I'm thinking that assuming properties
about
Isaac Dupree wrote:
Simon Peyton-Jones wrote:
...
No, constant folding is part of the compiler, I'm afraid, in the
module PrelRules.
Simon
_Constant_ folding is, but in GHC.Base there are rules like (unboxed)
multiplying by zero or one, or adding or subtracting zero, from an
unknown
Brandon S. Allbery KF8NH wrote:
On Aug 21, 2007, at 22:13 , Twan van Laarhoven wrote:
Other rules that could be interesting are:
forall a b. fromInteger a + fromInteger b = fromInteger (a + b)
I don't think this will work, a and b have to be the same type.
They are of the same type
Andrew Wagner wrote:
I've started a blog series on writing a chess engine in Haskell. I
just posted the second blog entry today:
http://sequence.complete.org/node/361
I suspect there's more work to be done on that function, though. It
seems like there should be a nice way to remove that flip in
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