Hi,
as for the nomenclature - mathematically the pattern
f^{-1} . g . f
is sometimes called conjugation [1]. One (trivial) type of occurrence is
data Foo a = Foo { unFoo :: a }
deriving Show
instance Functor Foo where
fmap f = Foo . f . unFoo
The under function from the lens library [2]
Brent Yorgey byorgey at seas.upenn.edu writes:
data Oneple a = Oneple a -- (or newtype)
(Oneple $ CustId 47) -- too verbose
This is what the OneTuple package is for:
Thank you Brent, and Ivan made the same suggestion.
Apart from
Can you please elaborate why this inconsistency is annoying and what's the
use of OneTuple?
Genuine question,
thanks.
On Fri, Aug 16, 2013 at 5:35 AM, AntC anthony_clay...@clear.net.nz wrote:
There's an annoying inconsistency:
(CustId 47, CustName Fred, Gender Male) -- threeple
Richard A. O'Keefe ok at cs.otago.ac.nz writes:
There are at least four different things that an Ord version might
mean:
- first sort a list, then eliminate duplicates
- sort a list eliminating duplicates stably as you go
(think 'merge sort', using 'union' instead of 'merge')
-
On Mon, Aug 19, 2013 at 5:40 AM, AntC anthony_clay...@clear.net.nz wrote:
...
Would double-parens be too wild an idea?:
... ((CustId 47)) `extend` (CustName Fred, Gender Male)
f ((CustId x)) = ...
instance C ((CustId Int)) ...
We'd have to avoid the double parens as in:
I recently encountered the following problem:
$ cabal install
Resolving dependencies...
Configuring array-0.4.0.1...
Building array-0.4.0.1...
Preprocessing library array-0.4.0.1...
Data/Array/IArray.hs:1:14:
This is definitely an issue with the array package not setting the right
minimum versions. You should email the maintainer.
On Aug 19, 2013 11:05 AM, Ketil Malde ke...@malde.org wrote:
I recently encountered the following problem:
On Sun, Aug 18, 2013 at 8:04 PM, Richard A. O'Keefe o...@cs.otago.ac.nzwrote:
The argument for twos-complement, which always puzzled me, is that the
other
systems have two ways to represent zero. I never found this to be a
problem,
not even for bitwise operations, on the B6700. I *did*
On Mon, Aug 19, 2013 at 11:43 AM, Kyle Miller kmill31...@gmail.com wrote:
Or, three other options: 1) make MIN_INT outside the domain of abs, 2)
make the range of abs be some unsigned int type, or 3) use Integer (i.e.,
use a type which actually represents integers rather than a type which can
Hi,
What is the proper way to implement a non-monadic function that checks
whether a given value is correct and gives a proper error message
otherwise ? What is the recommended option ?
* Either String a
check val
| valid val = Right val
| otherwise = Left errorMsg
* Maybe String
check
On Mon, Aug 19, 2013 at 9:48 PM, jabolo...@google.com wrote:
Hi,
Hello!
What is the proper way to implement a non-monadic function that checks
whether a given value is correct and gives a proper error message
otherwise ? What is the recommended option ?
I am not sure, what do you mean
On Mon, Aug 19, 2013 at 1:48 PM, jabolo...@google.com wrote:
What is the proper way to implement a non-monadic function that checks
whether a given value is correct and gives a proper error message
otherwise ? What is the recommended option ?
* Either String a
Preferred, usually, since
Hey,
Anyone knows what the proper channel for reporting bugs and asking
questions about wxHaskell is?
The github page https://github.com/wxHaskell/wxHaskell/wiki seems to
have issues disabled, and when I post to the wxHaskell user mailinglist,
it tells me that the list is moderated. But my
Yeah, non-monadic is not the best term... The problem is that it's
always so hard to communicate when you want to say a total function
that is not in the context of the IO monad. There should be a simple,
short name for these functions, so we can easily talk about them.
What ends up happening a
On Mon, Aug 19, 2013 at 2:09 PM, Brandon Allbery allber...@gmail.comwrote:
Alternatively, have you considered using your own ADT? `data Validity =
Success | Failure String` would give you more readable / comprehensible
code without needing to worry about assumptions or common usage.
Or
On Mon, Aug 19, 2013 at 02:20:23PM -0400, jabolo...@google.com wrote:
Yeah, non-monadic is not the best term... The problem is that it's
always so hard to communicate when you want to say a total function
that is not in the context of the IO monad. There should be a simple,
short name for
Joe Q headprogrammingc...@gmail.com writes:
This is definitely an issue with the array package not setting the right
minimum versions. You should email the maintainer.
Yes, that would be the thing to do, except that the maintainer is
librar...@haskell.org, whom I believe does not accept
I'd say that if you were in the context of the IO monad, maybe you'd
prefer to use exceptions instead of 'Either' or 'Maybe'.
Jose
On Mon, Aug 19, 2013 at 07:41:48PM +0100, Tom Ellis wrote:
On Mon, Aug 19, 2013 at 02:20:23PM -0400, jabolo...@google.com wrote:
Yeah, non-monadic is not the best
On Mon, Aug 19, 2013 at 2:59 PM, jabolo...@google.com wrote:
I'd say that if you were in the context of the IO monad, maybe you'd
prefer to use exceptions instead of 'Either' or 'Maybe'.
Even in IO, exceptions should be reserved for truly exceptional conditions
(of the program cannot safely
Except that people generally don't seem to agree what constitutes
'exceptional', even when disregarding the python world...
On Aug 19, 2013 9:24 PM, Brandon Allbery allber...@gmail.com wrote:
On Mon, Aug 19, 2013 at 2:59 PM, jabolo...@google.com wrote:
I'd say that if you were in the context
jabolo...@google.com,
MIME-Version: 1.0
Content-type: text/plain; charset=UTF-8
In-Reply-To:
CAKFCL4VfY-Dz3Xo9ZUZ_SmfRQ2nLGDLbovU=suf1-ssnqvs...@mail.gmail.com
References: CAKFCL4VfY-Dz3Xo9ZUZ_SmfRQ2nLGDLbovU=suf1-ssnqvs...@mail.gmail.com
quoth Brandon Allbery,
Even in IO, exceptions should be
On 8/19/2013 2:43 PM, Ketil Malde wrote:
Joe Q headprogrammingc...@gmail.com writes:
This is definitely an issue with the array package not setting the right
minimum versions. You should email the maintainer.
Yes, that would be the thing to do, except that the maintainer is
I agree that whether to use exceptions or not is a very debatable
subject and it is a grey area.
Still, in your Python example, I would like to point out that just
because something is common, it does not mean it is the right thing to
do. For example, something that some Java programmers were
On Mon, Aug 19, 2013 at 05:15:39PM -0400, jabolo...@google.com wrote:
But I would like to see more code move away from exceptions and into
types like Maybe or Either or other types defined for the
particular situation (as some people were suggesting in the beginning
of the thread). And the
On Mon, Aug 19, 2013 at 5:24 PM, Tom Ellis
tom-lists-haskell-cafe-2...@jaguarpaw.co.uk wrote:
On Mon, Aug 19, 2013 at 05:15:39PM -0400, jabolo...@google.com wrote:
But I would like to see more code move away from exceptions and into
types like Maybe or Either or other types defined for the
jabolo...@google.com :
I would like to see more code move away from exceptions and into
types like Maybe or Either or other types defined for the
particular situation (as some people were suggesting in the beginning
of the thread). And the reason for this it is because when you program
against
Some exceptions, e.g. in the traversal of deep structures may be and
ARE used as escaping continuations.
If I understand correctly, by escaping continuations you mean that
you can easily transfer control between the point where the exception
is raised and the exception handler.
If this is what
On 13-08-19 10:58 AM, Ketil Malde wrote:
b) the output isn't very helpful in tracking down the cause of this
problem, it claims that all these packages depend on array-0.4.0.1,
which is a lie. Somewhere, somehow, somethings depends on this (or at
least a newer version), but I have no clue how
Le 20/08/2013 00:19, jabolo...@google.com a écrit :
If I understand correctly, by escaping continuations you mean that
you can easily transfer control between the point where the exception
is raised and the exception handler.
If this is what you mean, you can achieve the same effect with
On Tue, Aug 20, 2013 at 12:25:44AM +0200, Jerzy Karczmarczuk wrote:
Le 20/08/2013 00:19, jabolo...@google.com a écrit :
If I understand correctly, by escaping continuations you mean that
you can easily transfer control between the point where the exception
is raised and the exception handler.
Has anyone given a go at a Category class and friends (including cartesian
and closed) with associated constraints (presumably using the
ConstraintKinds language extension)? I gave it a try a while back and
wasn't able to keep the signatures from getting very complicated.
Thanks, -- Conal
I've not seen such, Mike Izbicki has something related for most of the
other standard classes (though i've not looked closely at it myself)
http://hackage.haskell.org/package/ConstraintKinds-1.1.0.0
On Mon, Aug 19, 2013 at 6:45 PM, Conal Elliott co...@conal.net wrote:
Has anyone given a go at
Daniel F difrumin at gmail.com writes:
Can you please elaborate why this inconsistency is annoying and what's
the use of OneTuple?
Genuine question,
Hi Daniel, the main annoyance is the verbosity (of using a data type and
constructor), and that it no longer looks like a tuple.
The
On 20/08/2013, at 3:43 AM, Kyle Miller wrote:
On Sun, Aug 18, 2013 at 8:04 PM, Richard A. O'Keefe o...@cs.otago.ac.nz
wrote:
The argument for twos-complement, which always puzzled me, is that the other
systems have two ways to represent zero. I never found this to be a problem,
not even
On 20 August 2013 11:07, AntC anthony_clay...@clear.net.nz wrote:
Daniel F difrumin at gmail.com writes:
Can you please elaborate why this inconsistency is annoying and what's
the use of OneTuple?
Genuine question,
Hi Daniel, the main annoyance is the verbosity (of using a data type and
It seems to me that this is Identity given a different name. A bonus of
using Identity is that it won't introduce any new packages to the majority
of installations.
On 20/08/2013 1:17 PM, Ivan Lazar Miljenovic ivan.miljeno...@gmail.com
wrote:
On 20 August 2013 11:07, AntC
Mike Ledger eleventynine at gmail.com writes:
It seems to me that this is Identity given a different name. A bonus of
using Identity is that it won't introduce any new packages to the majority
of installations.
On 20/08/2013 1:17 PM, Ivan Lazar Miljenovic wrote:
...
isn't a single
It seems to me that this is Identity given a different name.
Close. But Identity is declared using newtype (just like monad
transformers), whereas OneTuple is declared with data (like the other
tuples).
This may or may not matter, depending on your use case.
On 20/08/2013 1:17 PM, Ivan Lazar
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