G'day all.
Quoting Johannes Waldmann waldm...@imn.htwk-leipzig.de:
you got this backwards: what some folks call idioms and (design) patterns
actually *is* FP, because it is just this: higher order functions.
And it's been there some decades (lambda calculus).
That also explains the absence of
G'day all.
Quoting Andrew Coppin andrewcop...@btinternet.com:
Heh. unsafePerformDoggeh# still amuses me...
I still have the original at full resolution of all the ones
I did (including unsafeDoggeh#), plus a couple that didn't make
it to the web site because they were deemed too obscure.
G'day all.
Quoting Dan Doel dan.d...@gmail.com:
Simon cat and Oleg cat are also missing, unfortunately.
http://andrew.bromage.org/pictures/simon.jpeg
http://andrew.bromage.org/pictures/oleg.jpeg
I can't remember if this one made it to the site or not:
G'day all.
Quoting José Romildo Malaquias j.romi...@gmail.com:
I am writing here to ask suggestions on how to annotate an ast with
types (or any other information that would be relevant in a compiler
phase) in Haskell.
This might help:
G'day all.
Quoting Ertugrul Soeylemez e...@ertes.de:
Do you realize at what level we are complaining?
Yes, we're complaining at the level of the frustrated idealist, which is
what many Haskell programmers are.
Cheers,
Andrew Bromage
___
G'day all.
Quoting Ertugrul Soeylemez e...@ertes.de:
In its highest level not fragmenting the user base means going back to
C++ and Windows.
Ha. You wouldn't say that if you were familiar with the current state
of C++ on Windows.
Since nobody has come out and admitted it, here's the real
G'day all.
Quoting Andrew Coppin andrewcop...@btinternet.com:
What the...?
Oh, I see. It uses another package to handle the tricky sorting and
searching stuff. Well, yeah, that would make the code a bit shorter...
;-)
Even so, it's not nearly as elegant to behold as, say, the quicksort
G'day all.
Quoting aditya siram aditya.si...@gmail.com:
I'm a little confused about this too. I've seen many functions defined like:
f x = (\s - ...)
which is a partial function because it returns a function and is the same as:
f x s = ...
Off the top of my head the State monad makes
G'day all.
Am 28.03.10 23:25, schrieb Ketil Malde:
Look, Günther, I'll give you credit for trying, but you might as well
accept the fact that using Haskell isn't going to get you laid.
For what it's worth, I got away with naming a daughter Miranda.
Cheers,
Andrew Bromage
G'day all.
Quoting Derek Elkins derek.a.elk...@gmail.com:
Ignoring bottoms the free theorem for fmap can be written:
If h . p = q . g then fmap h . fmap p = fmap q . fmap g
Setting p = id gives
h . id = h = q . g fmap h . fmap id = fmap q . fmap g
Using fmap id = id and h = q . g we get,
G'day all.
Quoting Dan Weston weston...@imageworks.com:
Ouch. That's what happens when you let a machine do the translation.
How about:
Once your good name is trashed, you can live unabashed.
Until you've lost your reputation, you never realize what a burden it was.
-- Margaret Mitchell
G'day all.
Quoting Richard O'Keefe o...@cs.otago.ac.nz:
These lines of Haskell code find the Zumkeller numbers up to 5000
in 5 seconds on a 2.2GHz intel Mac. The equivalent in SML took
1.1 seconds. Note that this just finds whether a suitable
partition exists; it does not report the
G'day all.
Quoting wren ng thornton w...@freegeek.org:
Sometimes in Haskell I've thought about how uniqueness typing would
make something faster, but in general all the plumbing associated with
it in Clean makes me feel like I'm writing systems-level code (i.e. C,
asm) instead of using a
G'day all.
Quoting John Meacham j...@repetae.net:
(+) seems to imply to me that the operator is non-associative. Something
like () or (+) would be better.
I tend to agree. Moreover, and I realise this may be a losing battle,
I want (++) to be the generic operator.
I understand the
G'day all.
On Tue, Jun 30, 2009 at 08:02:48PM -0400, Daniel Peebles wrote:
But we don't want to imply it's commutative either. Having something
bidirectional like or + feels more commutative than associative
to me.
Quoting John Meacham j...@repetae.net:
Not really, think of '++', which
G'day all.
Quoting Andrew Coppin andrewcop...@btinternet.com:
That's just scary. I was just in the middle of writing the exact same
thing! :-D (I read that very article...)
When you're both done, please compare with the implementation that's
been in Edison for about five years:
G'day Vasili.
This should do it:
remLookupFwd :: (ReVars m t) = SimplRe t - ReM m t (ReInfo t)
remLookupFwd re
= do fwd - gets resFwdMap
let { Just reinfo = fromJust (M.lookup re fwd) }
return reinfo
The FiniteMap lookup operation took its arguments in the opposite order.
G'day all.
Quoting Conal Elliott co...@conal.net:
The main objection I have to the negative process (can't be done) is that is
so often bogus. Proof by lack of imagination. I guess it works for
Richard, though not for Michael's architect, because Richard is able to
catch his bogus reasoning
G'day all.
Quoting Dan Weston weston...@imageworks.com:
Unless primesUpTo n goes from highest to lowest prime (ending in 2), I
don't see how sharing is possible (in either space or time) between
primesUpTo for different n.
Given that it's a mistake for a library to leak memory, there are
G'day all.
Quoting Eugene Kirpichov ekirpic...@gmail.com:
I'd suggest also
primesFrom :: Integer - [Integer]
This:
primes :: [Integer]
isn't as useful as you might think for a library, because it must, by
definition, leak an uncontrolled amount of memory. This:
primesUpTo :: Integer -
[Shifted to haskell-cafe.]
G'day all.
Quoting Benjamin L.Russell dekudekup...@yahoo.com:
According to the Merriam-Webster Online Dictionary, it is topoi (see
http://www.merriam-webster.com/dictionary/topos).
Topoi form a certain class of category. You can study topous, you can
prove
G'day all.
Quoting Gü?nther Schmidt gue.schm...@web.de:
my quest for data structures continues. Lately I came across Zippers.
Can anybody point be to some useful examples?
This is a good example, currently in use in GHC:
http://www.cs.tufts.edu/~nr/pubs/zipcfg-abstract.html
Cheers,
G'day all.
Quoting Lennart Augustsson lenn...@augustsson.net:
I think Data.Unique is horrible and should be banned.
It encourages a global variable style of programming that will just
bite you in the end.
In the sense that it doesn't give you anything that Monad.Supply
or
G'day all.
Quoting wren ng thornton w...@freegeek.org:
Most of the (particular) problems OO design patterns solve are
non-issues in Haskell because the language is more expressive.
...and vice versa. Some of the design patterns that we use in
Haskell, for example, are to overcome the fact
G'day all.
Quoting Jonathan Cast jonathancc...@fastmail.fm:
(By the way, you *do* have the equations
lift (return x) = return x
[...]
Right. And you could, at least in principle, implement return this
way in all monad transformers.
Cheers,
Andrew Bromage
G'day all.
On Mon, 2009-01-19 at 19:33 +, Andrew Coppin wrote:
My only problem with it is that it's called Bool, while every other
programming language on Earth calls it Boolean. (Or at least, the
languages that *have* a name for it...)
Jonathan Cast commented:
Except C++?
And
G'day all.
Quoting David Menendez d...@zednenem.com:
Are there any instances of Boolean that aren't isomorphic to Bool?
Sure. Two obvious examples:
- The lattice of subsets of a universe set, where or is union
and is intersection and not is complement with respect to the
universe.
-
G'day all.
I wrote:
- Intuitionistic logic systems.
- The truth values of an arbitrary topos (i.e. the points of the
subobject classifier).
Sorry, I misread the question. These are _not_ instances of Boolean
(or at least the latter isn't an instance in general).
Cheers,
Andrew Bromage
G'day all.
Quoting Gracjan Polak gracjanpo...@gmail.com:
I remember my early CS algebra courses. I met cool animals there: Group,
Ring, Vector Space. Those beasts were very strong, but also very calm at
the same time. Although I was a bit shy at first, after some work we
became friends.
I
G'day all.
Quoting John Goerzen jgoer...@complete.org:
If I see Appendable I can guess what it might be. If I see monoid, I
have no clue whatsoever, because I've never heard of a monoid before.
Any sufficiently unfamiliar programming language looks like line noise.
That's why every new
G'day all.
Dan Weston wrote:
Richard Feinman once said: if someone says he understands quantum
mechanics, he doesn't understand quantum mechanics.
But what did he know...
Presumably not quantum mechanics.
Cheers,
Andrew Bromage
___
G'day all.
Quoting Jeff Heard jefferson.r.he...@gmail.com:
I don't think that making Show a type class was a mistake.
I don't either. Two main reasons:
1. [Char] should not be shown ['l','i','k','e',' ','t','h','i','s'].
2. Default implementations of Show can break abstractions by leaking
G'day all.
Quoting Sebastian Sylvan syl...@student.chalmers.se:
Personally I find the current logo horrendous. I think it's ugly and
intimidating at the same time. I don't really care too much which one of the
proposals should win, just so long as I can weed out some of the ones I
really hate.
G'day all.
Thomas Davie wrote:
class IEngine a where
foo :: a - String
bar :: a - String - String
Apfelmus, Heinrich [EMAIL PROTECTED] replied:
You don't even need a type class, a simple data type is enough.
data Engine = Engine { foo :: IO (), bar :: String - IO () }
There is a
G'day all.
Quoting Bertram Felgenhauer [EMAIL PROTECTED]:
successors n b = sortWith (length . succs) . succs
[...]
successors n b = sortWith (length . (succs =) . succs) . succs
[...]
successors n b = sortWith (length . (succs =) . (succs =) .
succs) . succs
[...]
These improved
G'day all.
Quoting Don Stewart [EMAIL PROTECTED]:
So, team, anyone want to implement a Knight's Tour solver in a list
monad/list comprehension one liner? These little puzzles are made for
fast languages with backtracking monads
I conjecture that any one-liner won't be efficient.
Anyway,
G'day all.
Quoting Lennart Augustsson [EMAIL PROTECTED]:
People have been admitting to using Haskell like that for quite a while now.
I think it's an excellent use of Haskell as a DSEL host.
DSL is a proper superset of DSEL. Just saying.
Cheers,
Andrew Bromage
G'day all.
Quoting Tom Hawkins [EMAIL PROTECTED]:
Actually, Haskell is an excellent language for hard real-time
applications. At Eaton we're using it for automotive powertrain
control. Of course, the RTS is not running in the loop. Instead, we
write in a DSL, which generates C code for our
G'day all.
Quoting Achim Schneider [EMAIL PROTECTED]:
Considering that he's talking about a mud, I figure the grammar is a
quite straightforward
command = l[eft] | r[ight] | ... | t[ake] item | c[ast] spell
That is, I'd be very surprised if you even need more than two or three
characters
G'day all.
Quoting Achim Schneider [EMAIL PROTECTED]:
Considering that he's talking about a mud, I figure the grammar is a
quite straightforward
command = l[eft] | r[ight] | ... | t[ake] item | c[ast] spell
That is, I'd be very surprised if you even need more than two or three
characters
G'day all.
Quoting Mitchell, Neil [EMAIL PROTECTED]:
With rounding to the nearest even integer for 0.5's you get 6, otherwise
if you always round up you get 7. If you bias towards rounding up you
get a general upwards trend as numbers are rounded, which is bad, while
the even condition ensures
G'day all.
Quoting Daniel Fischer [EMAIL PROTECTED]:
Who does such horrible things?
Repeat after me: 1 is NOT a prime. Never, under no circumstances.
The definition of prime is well-understood standard terminology, but
that doesn't escape the fact that it's arbitrary and human-defined.
I'll
G'day all.
Henning Thielemann suggested:
In measured data the .5-case should be very rare - a null set?
However I assume that .5 happens more often in practice - because of
prior rounding, which was shown to be bad practice in this thread.
The usual case in floating point is usually not
G'day aoll.
Quoting Benjamin L.Russell [EMAIL PROTECTED]:
Interesting argument. At first I thought that the following
uncensored interview with Bjarne Stroustrup was a joke, but your
argument makes it seem all the more plausible:
That's not quite what I meant. What I meant is that Visual
G'day all.
On Sun, 2008-10-19 at 23:08 +0200, Achim Schneider wrote:
I'm asking 'cos I'm learning C++ and can't get the proper motivation to
do any program I can think of in it: If I need abstraction, I'm
thinking Haskell or Scheme, and if I'm thinking performance, C itself
more than suffices.
G'day all.
Quoting John Van Enk [EMAIL PROTECTED]:
I'm working on a Haskell based VPN. I can't think of any good names, so I'm
crowd sourcing it.
The naming of code is a difficult matter,
It isn't just one of your LAN party games;
You may think at first I'm as mad as a hatter
G'day all.
I asked:
But more to the point: Can it send email?
Quoting John Dorsey [EMAIL PROTECTED]:
Can you give an example of a use case?
I don't need one. It's not maximally flexible until it can send email.
Cheers,
Andrew Bromage
___
G'day all.
Quoting Lennart Augustsson [EMAIL PROTECTED]:
But I called it One.
That's a _terrible_ name. One, surely is (), just as Zero is Void.
While I'm at it, I really don't like the lexical syntax of comments.
Someone should fix that.
Cheers,
Andrew Bromage
G'day all.
Quoting Don Stewart [EMAIL PROTECTED]:
How about EDSLs for producing high assurance controllers, and other
robust devices they might need. I imagine the LHC has a good need for
verified software components...
On a related topic, I'm curious if anyone apart from me has been
G'day all.
Quoting John Dorsey [EMAIL PROTECTED]:
Contributions are welcome. The project could use a tutorial, and a
decent test suite. Strict singleton tuples are planned for the next
version.
I hope it has a Monad instance.
But more to the point: Can it send email?
Cheers,
Andrew
G'day all.
On Wed, Oct 1, 2008 at 3:42 PM, Jake McArthur [EMAIL PROTECTED] wrote:
Couldn't match expected type 'Deer' against inferred type 'Foot'
No instance for (Target Foot)
arising from use of `shoot' at SelfInflictedInjury.hs:1:0
Possible fix: add an instance declaration
G'day all.
Quoting Adrian Neumann [EMAIL PROTECTED]:
I often wonder how many cuts you need to divide a steak in n pieces.
One, if the cut is allowed to be curved and self-intersecting.
I think that the spirit of the problem, though is encapsulated in this
question: Given a circle, what is
G'day all.
Quoting Magnus Therning:
Recently I received an email with a question regarding the licensing
of a module I've written and uploaded to Hackage. I released it under
LGPL. The sender wondered if I would consider re-licensing the code
under BSD (or something similar) that would
G'day.
Quoting Jeremy Shaw [EMAIL PROTECTED]:
I have an expression data-type:
data Expr
= Quotient Expr Expr
| Product Expr Expr
| Sum Expr Expr
| Difference Expr Expr
| Lit Double
| Var Char
deriving (Eq, Ord, Data, Typeable, Read, Show)
And I want to write a
G'day all.
Quoting Richard A. O'Keefe [EMAIL PROTECTED]:
I'm currently arguing that lists:seq(1, 0) should be [],
not an exception. Oddly enough, I'm being beaten over the
head with Haskell, of all things.
[...]
Does anyone remember why the definition of enumFromTo is the way it is?
I
G'day.
Quoting wren ng thornton [EMAIL PROTECTED]:
I'm sure you know *why* it's an infinite list[1], but as for why that's
useful I can't say. It has the feel of a bug in implementation, though
it is ...consistent.
Right. I have no problem with [5,5..5] being logically an anamorphism,
but
G'day all.
Quoting Don Stewart [EMAIL PROTECTED]:
We promise both safety and efficiency.
We also provide (though don't promise) modularity, robustness
and correctness, which is not something that Java gives you out
of the box.
Cheers,
Andrew Bromage
G'day all.
Quoting Bjorn Buckwalter [EMAIL PROTECTED]:
I'd store the constants in a data structure along the lines of:
data AstroData a = AstroData
{ mu_Earth:: GravitationalParameter a
, leapSeconds :: LeapSecondTable
}
I would like to know if there is any consensus on what is
G'day all.
Quoting Richard A. O'Keefe [EMAIL PROTECTED]:
Just an idiot-level question: so these constants are subject
to revision, but *how often*?
Good question. For leap seconds:
- The data can change no quicker than once every 6 months.
- The shortest time between changes was 6
G'day all.
Quoting C.M.Brown [EMAIL PROTECTED]:
But isn't this exactly the point I was trying to make!? The whole point,
to me, in functional programming, is that we shouldn't have to worry about
the underlying implementation.
It is not exposing an underlying implementation detail to mandate
G'day all.
Quoting Thomas Davie [EMAIL PROTECTED]:
To be honest, ghc compiles things so fast (at least on any of
my systems) that I couldn't care less if it took 10 times as long (I would
however like some added convenience for that time spent)
Have you ever compiled GHC itself? Just
G'day.
Quoting C.M.Brown [EMAIL PROTECTED]:
However I saw no real argument for not having cyclic inclusions. You
say we shouldn't have to spend time writing hi-boot files, and yet
you also think
that GHC should not do it automatically. So we have to restrict all
programmers to never
G'day all.
Quoting Thomas Davie [EMAIL PROTECTED]:
I'm not sure that it does make a lot of sense -- we allow (mutually)
recursive functions, even though they come with an efficiency penalty.
Why should we not allow (mutually) recursive modules, even though they
too come with an efficiency
G'day all.
Quoting Thomas Davie [EMAIL PROTECTED]:
Why is separate compilation important?
I'm a little shocked that anyone on this list should have to ask this
question. Two people have asked it now.
The simplest answer is that unless your program fits in cache, it
takes longer to compile
G'day all.
Quoting Henning Thielemann [EMAIL PROTECTED]:
As far as I know the real difficulties come from mutually recursive
class definitions.
I wouldn't be surprised, because that's a more blatant instance of the
same problem. With classes and instances, there is no way to specify
whether
G'day all.
Quoting C.M.Brown [EMAIL PROTECTED]:
Yes, I saw that, thanks! I guess this is because it's hard to compile a
mutually recursive module...
It's because you don't need to declare the types of exported definitions.
Consider, this highly artificial example:
module A where
G'day.
Quoting Andrew Coppin [EMAIL PROTECTED]:
Right. So a Markov chain is actually a technical way of describing
something that's intuitively pretty obvious? (E.g., PPM compression
works by assuming that the input data is some sort of Markov chain with
as-yet unknown transition
G'day all.
Quoting Isaac Dupree [EMAIL PROTECTED]:
Luckily,
it is very often the case that your code will be better off anyway if
refactored to have less module recursion. (though not always.)
Nonetheless, I prefer not to leave the robustness of my code to luck.
Besides, if I liked
G'day all.
Quoting Achim Schneider [EMAIL PROTECTED]:
Please tell me that this isn't reversible.
It isn't reversible.
Cheers,
Andrew Bromage
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
G'day all.
Quoting Dan Piponi [EMAIL PROTECTED]:
For any specific monad, m, it's usually possible
to write a function m a - a.
Actually, it's true less than 50% of the time. In particular, it's
not true of any monad transformer.
Cheers,
Andrew Bromage
G'day all.
Quoting Andrew Coppin [EMAIL PROTECTED]:
The function (++) :: [x] - [x] - [x] has O(n) complexity.
That's not entirely true.
When you call (++), it does O(1) work. If you evaluate k cons cells.
it takes O(min(k,n)) work.
Cheers,
Andrew Bromage
G'day all.
Quoting John Peterson [EMAIL PROTECTED]:
Especially if SPJ decides to grow a beard. Unfortunately Paul is
now clean shaven so maybe Haskell is in trouble.
This explains why Clean never made it: Rinus Plasmeijer can't compete
with Phil Wadler in the beard department.
I should
G'day all.
Quoting Matt Amos [EMAIL PROTECTED]:
http://en.wikipedia.org/wiki/Longest_increasing_subsequence
The most efficient algorithm relies on destructive updates, so a
simple translation doesn't seem possible.
Given that it's based on binary search, you might like to try using a
binary
G'day all.
Quoting Jules Bean [EMAIL PROTECTED]:
Other solutions, such as class Functor m = Monad m are frequently discussed.
I see no H' ticket for it, though.
Then add it. :-)
You'll probably want to make it depend on Ticket #101, because making
class hierarchies more granular generally
G'day all.
Quoting Jinwoo Lee [EMAIL PROTECTED]:
Thanks everyone!
Now I think using IORef is the most practical way to do this.
Just a suggestion: Store it in a ReaderT instead of a StateT.
Cheers,
Andrew Bromage
___
Haskell-Cafe mailing list
G'day all.
Quoting Jeremy Shaw [EMAIL PROTECTED]:
I like to imagine it works like this:
bad static type dynamic typing good static typing.
More succinctly:
Algol Smalltalk ML
Or perhaps:
C Ruby Haskell
Cheers,
Andrew Bromage
___
G'day all.
Quoting Ashley Yakeley [EMAIL PROTECTED]:
GADT rhymes with cat. The d is silent, like the Danish godt, or
the German Stadt, or the American trademark Bundt.
I pronounce it so that it rhymes with ADT.
Cheers,
Andrew Bromage
___
G'day all.
Quoting Jeremy Apthorp [EMAIL PROTECTED]:
Clearly, this pronounciation is gay dee tea. I always new those
types were a bit queer.
Not that there's anything wrong with that.
Cheers,
Andrew Bromage
___
Haskell-Cafe mailing list
G'day all.
Quoting Andrew Coppin [EMAIL PROTECTED]:
And yet they commonly pop up in Haskell. Can anybody put their finger
on precisely why that is?
One of the reasons why advanced type hackery shows up a lot in Haskell
is that Haskell has never taken the easy way out.
When confronted with
G'day all.
Quoting askyle [EMAIL PROTECTED]:
Yup: bind f = f = id -- whence you can say (=) = flip bind
Ah, yes.
My point is that (as far as I can see) you cannot prove the properties of
bind by only assuming identity and associativity for (=).
One thing that may help is that if
G'day all.
Quoting askyle [EMAIL PROTECTED]:
So you're either not taking (=) as primitive or you're stating the
additional
property that there exists (=) such that f = g === (= g) . f
(from which you can easily show that (f . g) = h === (f = h) . g ).
If you wanted to prove that bind is
G'day all.
Quoting Adrian Hey [EMAIL PROTECTED]:
I take it you mean something like ..
Err... yes, I did.
Where's the Eq instance for OrdWrap?
Omitted for brevity.
This may or may not satisfy
the law: (compare a b) = EQ implies (a == b) = True. I think
everbody agrees about that, but I
G'day all.
Quoting Conor McBride [EMAIL PROTECTED]:
How depressing!
Sorry, I don't understand that. Quotient types are good, but they're
not the whole story. They just happen to be one use case with a
solid history behind them.
it's just that
we need to manage information hiding
G'day all.
Quoting Adrian Hey [EMAIL PROTECTED]:
If that's supposed it imply you think I'm in a minority of one I
don't think you've been following this thread very well.
Sorry, that was a bit of hyperbole.
Even the report uses the word equality in the prose.
Indeed, and the only
G'day all.
Adrian Hey wrote:
This might be a reasonable thing to say about *sortBy*, but not sort
as the ordering of equal elements should not be observable (for any
correct instance of Ord). It should be impossible to implement a
function which can discriminate between [a,a],[a,b],[b,a],[b,b]
G'day all.
Quoting askyle [EMAIL PROTECTED]:
If you use this presentation you also need the following law:
(a . b) = c = (a = c) . b
that is, compatibility with ordinary function composition. I like to call
this naturality, since it's instrumental in proving return and bind to be
natural
G'day all.
Quoting David Menendez [EMAIL PROTECTED]:
Adrian is arguing that compare a b == EQ should imply compare (f a) (f
b) == EQ for all functions f (excluding odd stuff). Thus, the problem
with your example would be in the Ord instance, not the sort function.
Understood, and the
G'day all.
Quoting Dan Weston [EMAIL PROTECTED]:
6.3.2 (The Ord Class):
The Ord class is used for totally ordered datatypes.
So... Double shouldn't be there, then?
As previously noted, nowhere is it even required that x /= y should
do the same thing as not (x == y).
Cheers,
Andrew Bromage
G'day all.
Quoting Derek Elkins [EMAIL PROTECTED]:
Of course, this is a concrete example using basic ideas of programming
and not some intuitive analogy. I feel comfortable working with
adjunctions, but I don't have some general analogy that I use.
I think this is important. The concept of
G'day all.
Quoting Cetin Sert [EMAIL PROTECTED]:
-- proposition
data Prp a = Var a
| Not (Prp a)
| Or (Prp a) (Prp a)
| And (Prp a) (Prp a)
| Imp (Prp a) (Prp a)
| Xor (Prp a) (Prp a)
| Eqv (Prp a) (Prp a)
| Cns Bool
G'day all.
Quoting Neil Mitchell [EMAIL PROTECTED]:
Yes, its the projection onto another type:
[] = Nothing
(x:xs) = Just (x, xs)
Also known as msplit:
http://www.haskell.org/haskellwiki/New_monads/MonadSplit
Cheers,
Andrew Bromage
___
G'day all.
Quoting Cetin Sert [EMAIL PROTECTED]:
It is astonishing to see that your version actually performs the worst (at
least on my machine).
On your example, I'm not surprised:
plong 0 = Var 0
plong n | even n= Or (Var n) (plong (n-1))
| otherwise = And (Var n) (plong
G'day all.
Richard A. O'Keefe wrote:
That's one of the warning signs I watch out for. Never compare floats for
equality is a sure sign of someone who thinks they know about
floats but don't.
Quoting Roman Leshchinskiy [EMAIL PROTECTED]:
Hmm. Personally, I've never seen an algorithm
G'day all.
Quoting Thorkil Naur [EMAIL PROTECTED]:
Finding the machine epsilon, perhaps, that is, the smallest
(floating point,
surely) number for which 1.0+machine_eps==1.0 would be a candidate?
The machine epsilon is the smallest relative separation between two
adjacent normalised
G'day all.
On Feb 10, 2008 3:40 PM, Mattes Simeon [EMAIL PROTECTED] wrote:
Though in comparison with C or C++ I can't figure out so clear the syntax.
Quoting Victor Nazarov [EMAIL PROTECTED]:
I think this is the most native way to do it in C++:
Herb Sutter and Andrei Alexandrescu will
G'day all.
On Feb 6, 2008 12:45 PM, Felipe Lessa [EMAIL PROTECTED] wrote:
I guess your parser is a monad transformer, so *maybe* the solution
is to require MonadError from the inner monad.
Quoting Bas van Dijk [EMAIL PROTECTED]:
Indeed my parser 'P t m a' is a monad transformer. I will
G'day all.
Quoting [EMAIL PROTECTED]:
Algol is dead. No
sense in disputing it.
And yet Delphi is still alive. So is Modula-3, though it tends to be
referred to as Java these days.
And, of course, Haskell is ensuring that Miranda will never really die.
Cheers,
Andrew Bromage
G'day all.
Quoting Neil Mitchell [EMAIL PROTECTED]:
It's nice to write functions in point free style:
f = sort . nub
But sometimes I have to add an extra case, on a certain value:
f [] = [1]
f = sort . nub
But now these equations have different arities, and its rejected by
Haskell.
I
G'day all.
Quoting Conal Elliott [EMAIL PROTECTED]:
That eta-expansion desugaring would lose sharing. Offhand, I don't know of
a desugaring that would do the trick and preserve sharing. Any ideas?
How about this?
f = let body = sort . nub
in \xs - case xs of
[] - [1]
G'day all.
Quoting Neil Mitchell [EMAIL PROTECTED]:
I don't believe that. I suspect the type system will mop these up.
As previously noted, anything involving undefined (thanks to seq) is
not equivalent.
While undefined is arguably uncommon, error most certainly isn't:
f1 (x:xs) = {-
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