BTW, I notice that your merges, like mine, are left-biased. This is a
useful property (my callers require it), and doesn't seem to cost
anything to implement, so maybe you could commit to it in the
documentation?
By left-biased I mean that when elements compare equal, pick the
leftmost one, e.g.
As well as books and reading material online, nowadays you can also find
video lectures...for example, the following was at the top of Googling
category theory video:
http://golem.ph.utexas.edu/category/2007/09/the_catsters_on_youtube.html
Cheers,
Mike.
Nick Rudnick wrote:
I haven't seen
On Thu, Feb 18, 2010 at 04:27, Nick Rudnick wrote:
I haven't seen anybody mentioning «Joy of Cats» by Adámek, Herrlich
Strecker:
It is available online, and is very well-equipped with thorough
explanations, examples, exercises funny illustrations, I would say best of
university lecture
Leon Smith wrote:
On Wed, Feb 17, 2010 at 6:58 AM, Heinrich Apfelmus
apfel...@quantentunnel.de wrote:
Ah, I meant to use the union' from your previous message, but I think
that doesn't work because it doesn't have the crucial property that the case
union (VIP x xs) ys = ...
does not
I've no idea about the GLPK system.
But, isn't it the case that you can transform any linear inequality into a
linear equality and a slack (or excess) variable? That's actually what you
*need to do* to turn the problem into the canonical form, so that simplex
can handle it.
2010/2/17 Daniel
Hello! The question is not about Haskell, but I don't know where else to ask.
In the book Computable functions by Vereshchagin and Shen it is said that it
is possible to invent a programming language such that each programming problem
has a unique solution in it. The author claims that this
Hi,
In fact it is not quite hard to see that such a numbering exists : just take
any numbering of all Turing machines, say {\phi_i}, then remove all indices i
such that there is ji such that \phi_j = \phi_i (equality is mathematically
correctly defined between functions from N to N).
Ah, and
Iteratee-parsec is a library which allows to have a parsec (3) parser in
IterateeG monad.
It contains 2 implementations:
- John Lato's on public domain. It is based on monoid and design with
short parsers in mind.
- Mine on MIT. It is based on single-linked mutable list. It seems to be
IM(H??)O, a really introductive book on category theory still is to be
written -- if category theory is really that fundamental (what I
believe, due to its lifting of restrictions usually implicit at
'orthodox maths'), than it should find a reflection in our every day's
common sense, shouldn't
I've needed something similar in the past.
I used it in the reflection library, and its present on its own on hackage
as 'tagged'.
http://hackage.haskell.org/packages/archive/tagged/0.0/doc/html/Data-Tagged.html
I talked a bit about using it here:
On 18 Feb 2010, at 14:48, Nick Rudnick wrote:
* the definition of open/closed sets in topology with the boundary
elements of a closed set to considerable extent regardable as facing
to an «outside» (so that reversing these terms could even appear
more intuitive, or «bordered» instead of
Am Donnerstag 18 Februar 2010 14:48:08 schrieb Nick Rudnick:
even in Germany, where the
term «ring» seems to originate from, since at least a century nowbody
has the least idea it once had an alternative meaning «gang,band,group»,
Wrong. The term Ring is still in use with that meaning in
Excerpts from Bardur Arantsson's message of Wed Feb 17 21:27:07 +0200 2010:
For sendfile, a timeout of 1 second would probably be fine. The *ONLY*
purpose of threadWaitWrite in the sendfile code is to avoid busy-waiting
on EAGAIN from the native sendfile.
Of course this will kill connections
On Thu, Feb 18, 2010 at 8:07 AM, Evan Laforge qdun...@gmail.com wrote:
And BTW again, here's something I've occasionally found useful:
-- | Handy to merge or sort a descending list.
reverse_compare :: (Ord a) = a - a - Ordering
reverse_compare a b = case compare a b of
LT - GT
EQ - EQ
Hi Edward
Does Tagged have a common synonym as its the 'opposite' of Const?
I thought I'd seen the same construction used with Strafunski /
StrategyLib, but if I did I can no longer find the examples.
Thanks
Stephen
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Haskell-Cafe mailing list
Hi Daniel,
;-)) agreed, but is the word «Ring» itself in use? The same about the
English language... de.wikipedia says:
« Die Namensgebung /Ring/ bezieht sich nicht auf etwas anschaulich
Ringförmiges, sondern auf einen organisierten Zusammenschluss von
Elementen zu einem Ganzen. Diese
Hi,
Your code forks off N threads to do HTTP response checking, then waits
for the reply (invokeThreads). Each thread (runHTTPThread) calls
curlGetResponse and *immediately* sends the answer back down the channel
to invokeThreads (checkAuthResponse) -- then waits for half a second
before
The trick is to use only non-negative variables for the equations.
(That's considered OK in linear programming. Though you may consider
it cheating.)
By the way, linear programming over rational numbers is in P.
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But, isn't it the case that you can transform any linear inequality into a
linear equality and a slack (or excess) variable? That's actually what you
*need to do* to turn the problem into the canonical form, so that simplex
can handle it.
Yes. The simplex is usually implemented in this form.
Am Donnerstag 18 Februar 2010 17:10:08 schrieb Nick Rudnick:
Hi Daniel,
;-)) agreed, but is the word «Ring» itself in use?
Of course, many people wear rings on their fingers.
Oh - you meant in the sense of gang/group?
It still appears as part of the name of some groups as a word of its own,
On Thu, Feb 18, 2010 at 7:48 AM, Nick Rudnick joerg.rudn...@t-online.dewrote:
IM(H??)O, a really introductive book on category theory still is to be
written -- if category theory is really that fundamental (what I believe,
due to its lifting of restrictions usually implicit at 'orthodox
On Tue, Feb 16, 2010 at 12:17 AM, Marc Weber marco-owe...@gmx.de wrote:
Any help on how to load the .h is greatly appreciated. I tried -i
with
path to the src directory but it didn't work (should it?).
Try -I -i is used for .hs files only (?).
This seems like a missing feature in
Hi Edward,
Nothing new under the sun it would seem :).
Perhaps these functions could be useful in the Tagged library?
on1 :: Tagged a v - Tagged (x a) v
on1 = retag
on2 :: Tagged a v - Tagged (x a x0) v
on2 = retag
on3 :: Tagged a v - Tagged (x a x0 x1) v
on3 = retag
on4 :: Tagged a v -
Hi Hans,
agreed, but, in my eyes, you directly point to the problem:
* doesn't this just delegate the problem to the topic of limit
operations, i.e., in how far is the term «closed» here more perspicuous?
* that's (for a very simple concept) the way that maths prescribes:
+ historical
Hi Alexander,
sry for being a bit thick, but how would this code be used?
I'm unable to figure out the application yet. Could you give some
examples how you use it?
Günther
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Haskell-Cafe@haskell.org
Gregg Reynolds wrote:
On Thu, Feb 18, 2010 at 7:48 AM, Nick Rudnick
joerg.rudn...@t-online.de mailto:joerg.rudn...@t-online.de wrote:
IM(H??)O, a really introductive book on category theory still is
to be written -- if category theory is really that fundamental
(what I believe, due
- Forwarded Message -
From: Michael Matsko msmat...@comcast.net
To: Nick Rudnick joerg.rudn...@t-online.de
Sent: Thursday, February 18, 2010 2:16:18 PM GMT -05:00 US/Canada Eastern
Subject: Re: [Haskell-cafe] Category Theory woes
Gregg,
Topologically speaking, the border
Am Donnerstag 18 Februar 2010 19:19:36 schrieb Nick Rudnick:
Hi Hans,
agreed, but, in my eyes, you directly point to the problem:
* doesn't this just delegate the problem to the topic of limit
operations, i.e., in how far is the term «closed» here more perspicuous?
It's fairly natural in
Am Donnerstag 18 Februar 2010 19:55:31 schrieb Nick Rudnick:
Gregg Reynolds wrote:
On Thu, Feb 18, 2010 at 7:48 AM, Nick Rudnick
joerg.rudn...@t-online.de mailto:joerg.rudn...@t-online.de wrote:
IM(H??)O, a really introductive book on category theory still is
to be written -- if
sry for being a bit thick, but how would this code be used?
I'm unable to figure out the application yet. Could you give some
examples how you use it?
Günther
So, the type (View view) -- ignoring class instances -- is basically
isomorphic to this (slightly simpler) type:
data View
Hi Mike,
so an open set does not contain elements constituting a border/boundary
of it, does it?
But a closed set does, doesn't it?
Cheers,
Nick
Michael Matsko wrote:
- Forwarded Message -
From: Michael Matsko msmat...@comcast.net
To: Nick Rudnick joerg.rudn...@t-online.de
On Feb 18, 2010, at 10:19 AM, Nick Rudnick wrote:
Back to the case of open/closed, given we have an idea about sets --
we in most cases are able to derive the concept of two disjunct sets
facing each other ourselves, don't we? The only lore missing is just
a Bool: Which term fits which
On 18 Feb 2010, at 20:20, Daniel Fischer wrote:
+ definition backtracking: «A closure operation c is defined by the
property c(c(x)) = c(x).
Actually, that's incomplete, ...
That's right, it is just the idempotency relation.
...missing are
- c(x) contains x
- c(x) is minimal among the
On 18 Feb 2010, at 19:19, Nick Rudnick wrote:
agreed, but, in my eyes, you directly point to the problem:
* doesn't this just delegate the problem to the topic of limit
operations, i.e., in how far is the term «closed» here more
perspicuous?
* that's (for a very simple concept) the way
Yves Parès wrote:
But there are two things that remain obscure:
First, there is my situation: int the main thread, I call to some C
functions binded through FFI. All of them are marked 'unsafe', except one,
which is internally supposed to make pauses with 'usleep'.
I then execute in another
Am Donnerstag 18 Februar 2010 21:47:02 schrieb Hans Aberg:
On 18 Feb 2010, at 20:20, Daniel Fischer wrote:
+ definition backtracking: «A closure operation c is defined by the
property c(c(x)) = c(x).
Actually, that's incomplete, ...
That's right, it is just the idempotency relation.
On Wed, Feb 17, 2010 at 10:23 PM, Sean Leather leat...@cs.uu.nl wrote:
-- oo :: (c - d) - (a - b - c) - a - b - d
oo :: (Category cat) = cat c d - (a - cat b c) - a - cat b d
oo = (.) . (.)
I think at NL-FP day 2008 at Utrecht somebody called '(.) . (.)' the
'boob' operator... it was late and
Hi all,
The darcs team would like to announce the immediate availability of darcs 2.4
release candidate 2. darcs 2.4 will contain many improvements and bugfixes
compared to darcs 2.3.1. Highlights are the faster operation of record, revert
and related commands, and the experimental interactive
On Thu, Feb 18, 2010 at 1:31 PM, Daniel Fischer daniel.is.fisc...@web.dewrote:
Am Donnerstag 18 Februar 2010 19:55:31 schrieb Nick Rudnick:
Gregg Reynolds wrote:
-- you agree with me it's far away from every day's common sense, even
for a hobby coder?? I mean, this is not «Head first
Nick,
That is correct. An open set contains no point on its boundary.
A closed set contains its boundary, i.e. for a closed set c, Closure(c) =
c.
Note that for a general set, which is neither closed or open (say the half
closed interval (0,1]), may contain points on
On 18 Feb 2010, at 22:06, Daniel Fischer wrote:
...missing are
- c(x) contains x
- c(x) is minimal among the sets containing x with y = c(y).
It suffices*) with a lattice L with relation = (inclusion in the
case
of sets) satifying
i. x = y implies c(x) = c(y)
ii. x = c(x) for all x in
Hi Mike,
of course... But in the same spirit, one could introduce a
straightforward extension, «partially bordered», which would be as least
as good as «clopen»... ;-)
I must admit we've come a little off the topic -- how to introduce to
category theory. The intent was to present some
On Feb 18, 2010, at 1:28 PM, Hans Aberg wrote:
It is a powerful concept. I think of a function closure as what one
gets when adding all an expression binds to, though I'm not sure
that is why it is called a closure.
Its because a monadic morphism into the same type carrying around data
Hans Aberg wrote:
On 18 Feb 2010, at 19:19, Nick Rudnick wrote:
agreed, but, in my eyes, you directly point to the problem:
* doesn't this just delegate the problem to the topic of limit
operations, i.e., in how far is the term «closed» here more perspicuous?
* that's (for a very simple
Hi Alexander,
my actual posting was about rename refactoring category theory;
closed/open was just presented as an example for suboptimal terminology
in maths. But of course, bordered/unbordered would be extended by e.g.
«partially bordered» and the same holds.
Cheers,
Nick
Alexander
On 18 Feb 2010, at 23:02, Nick Rudnick wrote:
418 bytes in my file system... how many in my brain...? Is it
efficient, inevitable?
Yes, it is efficient conceptually. The idea of closed sets let to
topology, and in combination with abstractions of differential
geometry led to cohomology
Gregg Reynolds wrote:
On Thu, Feb 18, 2010 at 1:31 PM, Daniel Fischer
daniel.is.fisc...@web.de mailto:daniel.is.fisc...@web.de wrote:
Am Donnerstag 18 Februar 2010 19:55:31 schrieb Nick Rudnick:
Gregg Reynolds wrote:
-- you agree with me it's far away from every day's common
On Feb 18, 2010, at 2:08 PM, Nick Rudnick wrote:
my actual posting was about rename refactoring category theory;
closed/open was just presented as an example for suboptimal
terminology in maths. But of course, bordered/unbordered would be
extended by e.g. «partially bordered» and the same
Ben Franksen wrote:
You can leave them unsafe if you are sure that
1) they do not call (back) any function in your program
2) they do not block (or not long enough that it bothers you)
Otherwise they are no less safe that the safe calls. If (1) is not
fulfilled bad things might (that is,
Nick,
Actually, clopen is a set that is both closed and open. Not one that is
neither. Except in the case of half-open intervals, I can't remember talking
much in topology about sets with a partial boundary.
Category theory-wise. No one seems to have mentioned MacLane's Categories for
the
Hans Aberg wrote:
On 18 Feb 2010, at 23:02, Nick Rudnick wrote:
418 bytes in my file system... how many in my brain...? Is it
efficient, inevitable?
Yes, it is efficient conceptually. The idea of closed sets let to
topology, and in combination with abstractions of differential
geometry led
On Feb 19, 2010, at 3:55 AM, Daniel Fischer wrote:
Am Donnerstag 18 Februar 2010 14:48:08 schrieb Nick Rudnick:
even in Germany, where the
term «ring» seems to originate from, since at least a century nowbody
has the least idea it once had an alternative meaning
«gang,band,group»,
Wrong.
Alexander Solla wrote:
On Feb 18, 2010, at 2:08 PM, Nick Rudnick wrote:
my actual posting was about rename refactoring category theory;
closed/open was just presented as an example for suboptimal
terminology in maths. But of course, bordered/unbordered would be
extended by e.g. «partially
On Feb 19, 2010, at 11:22 AM, Hans Aberg wrote:
As for the naming problem, it is more of a linguistic problem: the
names were somehow handed by tradition, and it may be difficult to
change them. For example, there is a rumor that kangaroo means I
do not understand in a native language;
Am Freitag 19 Februar 2010 00:24:23 schrieb Richard O'Keefe:
On Feb 19, 2010, at 3:55 AM, Daniel Fischer wrote:
Am Donnerstag 18 Februar 2010 14:48:08 schrieb Nick Rudnick:
even in Germany, where the
term «ring» seems to originate from, since at least a century nowbody
has the least idea
Daniel Fischer wrote:
Am Donnerstag 18 Februar 2010 19:19:36 schrieb Nick Rudnick:
Hi Hans,
agreed, but, in my eyes, you directly point to the problem:
* doesn't this just delegate the problem to the topic of limit
operations, i.e., in how far is the term «closed» here more perspicuous?
On Thu, Feb 18, 2010 at 2:32 AM, Evan Laforge qdun...@gmail.com wrote:
By purest coincidence I just wrote the exact same function (the simple
mergeAll', not the VIP one). Well, extensionally the same...
intensionally mine is 32 complicated lines and equivalent to the 3
line mergeAll'. I even
On Feb 18, 2010, at 4:49 PM, Nick Rudnick wrote:
Why does the opposite work well for computing science?
Does it? I remember a peer trying to convince me to use the factory
pattern in a language that supports functors. I told him I would do
my task my way, and he could change it later
Hi Alexander,
please be more specific -- what is your proposal?
Seems as if you had more to say...
Nick
Alexander Solla wrote:
On Feb 18, 2010, at 4:49 PM, Nick Rudnick wrote:
Why does the opposite work well for computing science?
Does it? I remember a peer trying to convince me to
On Thu, Feb 18, 2010 at 3:07 AM, Evan Laforge qdun...@gmail.com wrote:
BTW, I notice that your merges, like mine, are left-biased. This is a
useful property (my callers require it), and doesn't seem to cost
anything to implement, so maybe you could commit to it in the
documentation?
Also, I
Hi,
wow, a topic specific response, at last... But I wish you would be more
specific... ;-)
A *referrer* (object) refers to a *referee* (object) by a *reference*
(arrow).
Doesn't work for me. Not in Ens (sets, maps), Grp (groups, homomorphisms),
Top (topological spaces, continuous
On Thu, Feb 18, 2010 at 5:22 PM, Leon Smith leon.p.sm...@gmail.com wrote:
On Thu, Feb 18, 2010 at 3:07 AM, Evan Laforge qdun...@gmail.com wrote:
BTW, I notice that your merges, like mine, are left-biased. This is a
useful property (my callers require it), and doesn't seem to cost
anything to
On Feb 19, 2010, at 2:48 PM, Nick Rudnick wrote:
Please tell me the aspect you feel uneasy with, and please give me
your opinion, whether (in case of accepting this) you would rather
choose to consider Human as referrer and Int as referee of the
opposite -- for I think this is a deep
I'm happy to announce the release of vty-ui 0.3.
Get it from Hackage:
http://hackage.haskell.org/package/vty-ui
Or get the source with darcs:
http://repos.codevine.org/vty-ui
Project homepage:
http://codevine.org/vty-ui/
This version of vty-ui features a richer rendering engine,
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