On Thu, Nov 29, 2012 at 05:49:53PM +, Jon Fairbairn wrote:
Ben Franksen ben.franksen at online.de writes:
just wanted to drop by to say how much I like the new lambda case
extension.
I use it all the time and I just *love* how it relieves me from conjuring
up
dummy variables,
To avoid retaining a large lazy data structure in memory it is useful to
hide it behind a function call. Below, many is used twice. It is hidden
behind a function call so it can be garbage collected between uses. That's
good. When compiling with -O it seems that GHC 7.4.1 decides to keep it
in
On Sun, Feb 24, 2013 at 07:12:24PM +0100, Joachim Breitner wrote:
You should try:
million :: () - Int
million _ = 10 ^ (6 :: Int)
many :: () - [Int]
many x = [1..million x]
Thanks Joachim, but that doesn't work either.
Tom
% cat thunkfail.hs
{-# OPTIONS_GHC -fno-warn-unused-binds
On Sun, Feb 24, 2013 at 06:25:56PM +, Don Stewart wrote:
If you explicitly rely on this not happening, turn it off:
$ ghc -O2 -fno-full-laziness --make A.hs -rtsopts -fforce-recomp
[1 of 1] Compiling Main ( A.hs, A.o )
Linking A ...
$ time ./A +RTS -M750k
On Tue, Feb 26, 2013 at 10:00:32AM -, o...@okmij.org wrote:
Tom Ellis wrote:
To avoid retaining a large lazy data structure in memory it is useful to
hide it behind a function call. Below, many is used twice. It is hidden
behind a function call so it can be garbage collected between
On Fri, Mar 08, 2013 at 08:53:15PM -0800, Edward Z. Yang wrote:
Are these equivalent? If not, under what circumstances are they not
equivalent? When should you use each?
evaluate a return b
[...]
- Use 'evaluate' when you mean to say, Evaluate this thunk to HNF
before doing
The -ddump-simpl output below doesn't contain a case corresponding to the
seq in sum', but the -ddump-prep does. Isn't the output from simpl the
input to prep? If so, where does the case reappear from? If not, how are
simpl and prep related?
It seems to have something to do with Str=DmdType SS
On Thu, Mar 14, 2013 at 10:43:14PM +, Simon Peyton-Jones wrote:
| -Original Message-
| From: Tom Ellis
| The -ddump-simpl output below doesn't contain a case corresponding to the
| seq in sum', but the -ddump-prep does. Isn't the output from simpl the
| input to prep? If so
On Fri, Mar 08, 2013 at 08:53:15PM -0800, Edward Z. Yang wrote:
Are these equivalent? If not, under what circumstances are they not
equivalent? When should you use each?
evaluate a return b
a `seq` return b
return (a `seq` b)
Furthermore, consider:
[...]
- Does the
On Thu, Apr 04, 2013 at 11:02:34AM +, Johannes Waldmann wrote:
My feeling is that mathematicians use this principle of leaving out
some of the quantifiers and putting some others in the wrong place
as a cultural entry barrier to protect their field from newbies.
Albert showed an example
On Thu, Apr 04, 2013 at 01:15:27PM +, Johannes Waldmann wrote:
Tom Ellis tom-lists-haskell-cafe-2013 at jaguarpaw.co.uk writes:
I didn't see an example of quantifiers in the wrong place.
The example was:
every x satisfies P(x,y) for some y
Oh I see. I interpreted that as lack
On Thu, Apr 04, 2013 at 06:29:51PM -0400, Albert Y. C. Lai wrote:
You may think you know what's wrong, but you don't actually know
until you know how to clarify to the beginners. Note: harping on the
word any does not clarify, for the beginners exactly say this:
Yeah, t can be *any* type,
On Sat, Apr 06, 2013 at 05:14:48PM -0400, Albert Y. C. Lai wrote:
On 13-04-05 04:56 AM, Tom Ellis wrote:
any is very ambiguous. Doesn't the problem go away if you replace it with
all?
Yes, that is even better.
The world would be simple and elegant if it did things your way, and
would
On Wed, Apr 10, 2013 at 03:38:35PM +0100, Barak A. Pearlmutter wrote:
In fiddling around with some numeric code in Haskell, I noticed some
issues. Basically, you get warnings if you write
energy mass = mass * c^2
but not if you write
energy mass = mass * c * c
Numeric typeclasses
On Wed, Apr 10, 2013 at 11:20:15PM +0400, Aleksey Khudyakov wrote:
This IS rather annoying problem for numeric code. Raising value to positive
power is quite common operation yet ^ operator generally couldn't be used
because it leads to warning about type defaulting (rightfully) and one
wants
On Thu, Apr 11, 2013 at 12:56:05AM +0100, Barak A. Pearlmutter wrote:
... in most of the cases I do want this warnings. It's possible to get
something default to Integer when it should be Int. There are only few
cases when it's not appropriate. Only ^ and ^^ with literals I think
There
On Thu, Apr 11, 2013 at 12:49:40PM +1200, Richard A. O'Keefe wrote:
On 10/04/2013, at 2:45 PM, o...@okmij.org wrote:
... unsafeInterleaveST is really unsafe ...
import Control.Monad.ST.Lazy (runST)
import Control.Monad.ST.Lazy.Unsafe (unsafeInterleaveST)
import Data.STRef.Lazy
On Tue, Apr 16, 2013 at 10:17:48AM +0100, Tom Crayford wrote:
I kept on running into this thing where I was calling error in quickcheck
to get good error messages about the things I was comparing. In Java land,
this stuff is handled by Hamcrest: a library for composable assertions with
good
On Tue, Apr 16, 2013 at 01:53:19PM +0100, Oliver Charles wrote:
On 04/16/2013 01:47 PM, Lyndon Maydwell wrote:
You could do:
runKleisli . mconcat . map Kleisli :: Monoid (Kleisli m a b) = [a
- m b] - a - m b
Would that work for you?
I can't find an instance for Monoid (Kleisli m a b) in
On Fri, Apr 19, 2013 at 11:42:14AM +0300, Boris Lykah wrote:
The full description of the configuration options is available at
http://hackage.haskell.org/packages/archive/groundhog-th/0.3.0/doc/html/Database-Groundhog-TH.html
Hi Boris, the docs for 0.3.0 don't currently seem to exist.
Tom
On Tue, Apr 23, 2013 at 09:36:04AM +0200, Petr Pudlák wrote:
I tested it on GHC 6.12.1, which wasn't affected by the recent ackermann
bug, but still it leaks memory.
I tested it on GHC 7.4.1 and I don't see any space leak.
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On Thu, May 02, 2013 at 09:26:15PM +0800, Adrian May wrote:
How about the Haskell Platform? Is that ancient history? Certainly not: it
doesn't compile on anything but the very newest GHC. Not 7.4.1 but 7.4.2.
I'm uninformed in such matters, but from
On Thu, May 02, 2013 at 10:36:18PM +0800, Adrian May wrote:
Please would somebody explain to me what getPackageId did to incriminate
itself?
What's getPackageId? It does not appear in the WASH source.
Tom
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On Thu, May 02, 2013 at 11:10:33PM +0800, Adrian May wrote:
What's getPackageId? It does not appear in the WASH source.
It's in Setup.lhs, in WashNGo.
Which source of WashNGo are you using? It doesn't appear in either of these
versions:
http://hackage.haskell.org/package/WashNGo-2.12
On Thu, May 02, 2013 at 11:23:12PM +0800, Adrian May wrote:
Which source of WashNGo are you using? It doesn't appear in either of
these
versions:
http://hackage.haskell.org/package/WashNGo-2.12
http://hackage.haskell.org/package/WashNGo-2.12.0.1
On Thu, May 02, 2013 at 11:35:27PM +0800, Adrian May wrote:
I get a 403 FORBIDDEN on that. How did you get it?
I guess you just gotta know the right people ;-)
I attached the tarball. Don't say you got it from me, OK.
That tarball still doesn't contain the string getPackageId.
You're
On Fri, May 03, 2013 at 09:34:21PM +0800, Adrian May wrote:
I never doubted that people add new stuff for valid reasons. What I'm
interested in is whether or not it could have been done without breaking
anything. But having thought about it for a while, I'm tending to think
that version
On Sun, May 05, 2013 at 10:46:23PM +0200, Alberto G. Corona wrote:
The case of WASH is a pity. Architecturally It was more advanced that many
recent haskell web frameworks. The package would have been a success with
little changes in the DSL syntax.
Could you briefly summarise the difference
On Mon, May 13, 2013 at 02:08:26PM -0800, Christopher Howard wrote:
instance Integral a = Coord2 (CircAppr a) where
coords2 (CircAppr divns ang rad) =
let dAng = 2 * pi / (fromIntegral divns) in
let angles = map (* dAng) [0..divns] in
undefined -- To be coded...
Your
On Mon, May 13, 2013 at 11:43:41PM +0100, Tom Ellis wrote:
On Mon, May 13, 2013 at 02:08:26PM -0800, Christopher Howard wrote:
instance Integral a = Coord2 (CircAppr a) where
coords2 (CircAppr divns ang rad) =
let dAng = 2 * pi / (fromIntegral divns) in
let angles = map
Suppose I have a Category C
import Prelude hiding ((.), id)
import Control.Category
data C a b
instance Category C where
(.) = undefined
id = undefined
which has products in the sense that there exists a factors function
with suitable properties
factors :: C a (b, c) - (C
On Tue, May 21, 2013 at 06:18:16PM +0800, Adrian May wrote:
* can I use postgres from Haskell?
I've been successfully using
http://hackage.haskell.org/package/postgresql-simple
It's fine so far except it throws exceptions willy-nilly. (I find
exceptions very un-Haskell but some people
On Mon, May 27, 2013 at 02:10:28PM -0400, Clark Gaebel wrote:
I'd be down for helping update packages when the time comes.
As am I, for what it's worth.
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On Tue, May 28, 2013 at 04:42:35PM +0200, Johannes Gerer wrote:
By the same argument, could'nt I say, that any type class (call it
AnyClass) can do everything a Monad can:
instance AnyClass m = Monad (Cokleilsi m ())
That doesn't say that AnyClass can do anything a Monad can. AnyClass m =
On Tue, May 28, 2013 at 05:21:58PM +0200, Johannes Gerer wrote:
That makes sense. But why does
instance Monad m = ArrowApply (Kleisli m)
show that a Monad can do anything an ArrowApply can (and the two are
thus equivalent)?
I've tried to chase around the equivalence between these two
On Tue, May 28, 2013 at 09:09:48PM +0200, Johannes Gerer wrote:
What about these two very simple type classes. Are they equivalent?
[...]
class Pointed f where
pure :: a - f a
class Unit f where
unit :: f a a
newtype UnitPointed f a = UnitPointed f a a
instance Unit f = Pointed
On Tue, May 28, 2013 at 11:22:22PM +0200, Johannes Gerer wrote:
I have to ask, why was plausability and looking at the actual definition
(not just the types) not important for the other examples.
It would also be important to check the definitions in the other examples
too, but it's hard enough
On Tue, Jun 04, 2013 at 04:01:37PM +0200, Peter Simons wrote:
How is this a problem?
If you're representing text, use 'text'.
If you're representing a string of bytes, use 'bytestring'.
If you want an array of values, think c++ and use 'vector'.
the problem is that all those
On Tue, Jun 04, 2013 at 11:23:16PM +0200, Peter Simons wrote:
On Tue, Jun 04, 2013 at 04:01:37PM +0200, Peter Simons wrote:
If you're representing text, use 'text'.
If you're representing a string of bytes, use 'bytestring'.
If you want an array of values, think c++ and use
On Fri, Jun 07, 2013 at 07:08:19AM -0700, David Banas wrote:
op ::
Newtypehttp://hackage.haskell.org/packages/archive/newtype/0.2/doc/html/Control-Newtype.html#t:Newtype
n
o = (o - n) - n -
oSourcehttp://hackage.haskell.org/packages/archive/newtype/0.2/doc/html/src/Control-Newtype.html#op
to
use a type variable from the top level within the body of a function. If
you use op and specify a particular constructor then you don't have a
variable but a concrete instance of a type. But maybe I'm missing some more
powerful way this can be used ...
Tom
On Jun 7, 2013 2:53 PM, Tom Ellis
On Mon, Jun 10, 2013 at 05:41:05PM +0530, Zed Becker wrote:
Haskell, is arguably the best example of a design-by-committee language.
The syntax is clean and most importantly, consistent. The essence of a
purely functional programming is maintained, without disturbing its real
world capacity.
On Mon, Jun 10, 2013 at 03:21:28PM +0200, Ertugrul Söylemez wrote:
Tom Ellis tom-lists-haskell-cafe-2...@jaguarpaw.co.uk wrote:
Hear hear! Hopefully we, the Haskell community, will be able to
support this endevour with our time and efforts.
Every Haskell user does this in their own way
On Mon, Jun 10, 2013 at 05:44:26PM +0400, MigMit wrote:
It really sounds rude, to demand promises from somebody who just gave you a
big present.
Without wishing to preempt Zed Becker, I interpreted his email as an
expression of delight at how well Haskell has been designed and of hope that
it
On Sun, Jun 16, 2013 at 01:03:48PM -0700, bri...@aracnet.com wrote:
wireframe :: Double - Double - Double - IO ()
wireframe wx wy wz = do
-- yz plane
renderPrimitive LineLoop $ do
vertex $ Vertex3 0.0 0.0 0.0
vertex $ Vertex3 0.0 wy 0.0
On Sun, Jun 16, 2013 at 05:22:59PM -0700, bri...@aracnet.com wrote:
Vertex3 takes three arguments, all of which must be of the same instance of
VertexComponent. Specifying GLdoubles in the signature of wireframe
specifies the types in the last three calls to Vertex3, but (0.0 ::
GLdouble)
On Sat, Jun 22, 2013 at 04:26:14AM -0500, Brian Lewis wrote:
Say you write
data Callback = Error ... | ...
[...]
Then, later, you write
data Error = ...
[...]
They're both good names, but there's a conflict.
What do you mean by a conflict? That's fine as far as the compiler is
concerned
I feel I may be doing a lot of programming with Arrows in the near future.
Currently I'm delighted that Arrow notation[1] exists. It makes using
Arrows much less painful.
Are there any best-practices I should be aware of with Arrows? Or is it
just a case of getting on with it?
Tom
1.
Hi Ertugul. Thanks for taking the time to write me an in-depth reply! I
have a few comments and a question.
On Sat, Jun 22, 2013 at 03:36:15PM +0200, Ertugrul Söylemez wrote:
Tom Ellis tom-lists-haskell-cafe-2...@jaguarpaw.co.uk wrote:
Are there any best-practices I should be aware
On Mon, Jun 24, 2013 at 08:02:17AM -0700, Mark Lentczner wrote:
And yet, just four fonts make up over 75% of the sample - and two of those
are essentially identical!
Inconsolata and Consolas?
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On Mon, Jul 01, 2013 at 05:18:39PM +1200, Richard A. O'Keefe wrote:
On 1/07/2013, at 1:04 PM, Richard Cobbe wrote:
I should have been clearer in my original question: I'm curious about what
to do when a multi-argument function application gets split across lines.
That wiki page dicsusses
On Mon, Jul 01, 2013 at 05:07:00PM +0200, Vlatko Basic wrote:
Hello Cafe!
I had a (simplified) record
data P = P {
a :: String,
b :: String,
c :: IO String
} deriving (Show, Eq)
but to get automatic deriving of 'Show' and 'Eq' for 'data P' I have
created 'newtype
Yeah I'm getting stuff from j...@eukor.com every time I post.
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On Tue, Jul 02, 2013 at 03:03:08PM +0200, Vlatko Basic wrote:
Is there a nicer way to extract the 'IO String' from 'IOS',
without 'case' or without pattern matching the whole 'P'?
newtype IOS = IOS (IO String)
data P = P {
getA :: String,
getB :: String,
getC :: IOS
} deriving
On Mon, Jul 08, 2013 at 09:55:08PM -0700, Kirill Zaborsky wrote:
Brian, I think it would be better to provide your email in the thread. E.g.
from http://www.haskell.org/pipermail/haskell-cafe/2013-July/109061.html I
can only reply to the maillist. I'm answering now through Google Groups
On Mon, Jul 15, 2013 at 07:19:12AM -0700, Kirill Zaborsky wrote:
http://www.haskell.org/hoogle/ responds with some ELF file.
After running strings on it, it does seem to be (at least part of) the
hoogle binary.
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On Tue, Jul 16, 2013 at 04:57:59PM -0400, Michael Orlitzky wrote:
This all works great, except that when there's 20 or so options, I
duplicate a ton of code in the definition of OptionalCfg. Is there some
pre-existing solution that will let me take a Cfg and create a new type
with Cfg's fields
On Mon, Jul 22, 2013 at 12:02:54AM -0800, Christopher Howard wrote:
A binding is memoized if, ignoring everything after the equals sign,
it looks like a constant.
[...]
Thanks. That's very helpful to know. Yet, it seems rather strange and
arbitrary that f x = ... and f = \x - ... would be
On Mon, Jul 22, 2013 at 07:52:06PM +1200, Chris Wong wrote:
A binding is memoized if, ignoring everything after the equals sign,
it looks like a constant.
In other words, these are memoized:
[...]
f = \x - x + 1
[...]
and these are not:
f x = x + 1
In what sense is the former
On Mon, Jul 22, 2013 at 04:16:19PM +0200, Andreas Abel wrote:
In general, I would not trust such compiler magic, but just let-bind
anything I want memoized myself:
memoized_fib :: Int - Integer
memoized_fib x = fibs !! x
where fibs = map fib [0..] -- lazily computed infinite list
On Mon, Jul 22, 2013 at 04:04:33PM -0700, wren ng thornton wrote:
Consider rather,
f1 = let y = blah blah in \x - x + y
f2 x = let y = blah blah in x + y
The former will memoize y and share it across all invocations of f1;
whereas f2 will recompute y for each invocation.
On Wed, Jul 24, 2013 at 10:06:59AM +0200, Andreas Abel wrote:
For -O1 and greater, ghc seems to see that x is not mentioned in the
where clauses and apparently lifts them out. Thus, for -O1..
memoized_fib is also memoizing. (I ran it, this time ;-) !)
Right, I believe this is the full
On Thu, Jul 25, 2013 at 07:34:55PM +1200, Richard A. O'Keefe wrote:
It's a queer thing, I always feel that the advice about
keeping function bodies small is patronising nonsense for
beginners and that *my* code is perfectly readable no matter
how big it is, but end up wishing that *other*
On Wed, Jul 31, 2013 at 09:45:50AM +0600, Alexey Uimanov wrote:
Hello, haskellers. This is the first release of HDBI (Haskell Database
Independent interface).
Hi, thanks for this Alexey. It's great that there is continued development
of this really important infrustructure for Haskell.
I have
On Wed, Jul 31, 2013 at 01:22:42PM +0600, Alexey Uimanov wrote:
I also have the idea do not throw the exceptions in IO but return (Either
SqlError a) from all the Connection and Statement methods for safe data
processing. What do you think about ?
I feel very strongly that you should use
On Wed, Jul 31, 2013 at 05:28:02PM +0600, Alexey Uimanov wrote:
The rationale is that the low-level database interface accepts parameters
directly instead of inserting them inside the query manually.
[...]
Low-level database interface knows better how to work with parameters, so
the driver
On Thu, Aug 01, 2013 at 01:25:22PM +0100, Richard Evans wrote:
It still doesn't work when I try it.
What URL are you using? http://www.haskell.org/hoogle works fine for me.
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On Tue, Aug 06, 2013 at 10:03:04AM +0200, J. Stutterheim wrote:
`putStrLn Hi` is not a pure value...
Why not?
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On Tue, Aug 06, 2013 at 04:26:05PM +0200, Jerzy Karczmarczuk wrote:
1. First, it is not true that you can do with, say, (printStr Ho!
) whatever you want. In fact, you can do almost nothing with it. You
can transport it as such, and you can use it as the argument of
(=).
I don't think this
you
run it.
What do you mean by the same thing? You cannot compare 'them' in
any reasonable sense.
This, the impossibility to check putStr c == putStr c, is btw, a
refutation of the claim by Tom Ellis that you can do even less with
(). The void object is an instance of the Eq and Ord classes
On Thu, Aug 08, 2013 at 11:38:08AM +0200, Jerzy Karczmarczuk wrote:
Tom Ellis:
If I were writing a Haskell compiler I could certainly define 'IO' to be a
datatype that would allow me to compare 'putStr c' to itself. The
comparison could not be of operational equivalence, but it would still
On Thu, Aug 08, 2013 at 08:41:25AM -0400, Jake McArthur wrote:
I don't know what the denotation for this would be, but I can't think of
any reasonable ones for which I can write (==) to respect the denotation.
For example, is set A, then set B equal to set B, then set A?
[...]
I'm a bit lost
On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
One could simply implement IO as a free monad
Interesting. I wonder how.
See [1] for an explanation of free monads in general. For IO in particular,
define a functor
data IOF a = GetChar (Char - a) | PutChar Char a | ...
On Thu, Aug 08, 2013 at 05:23:50PM +0100, Oliver Charles wrote:
On 08/08/2013 05:05 PM, Tom Ellis wrote:
On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
One could simply implement IO as a free monad
Interesting. I wonder how.
See [1] for an explanation of free
On Thu, Aug 08, 2013 at 06:25:12PM +0200, Daniel Trstenjak wrote:
See [1] for an explanation of free monads in general. For IO in particular,
define a functor
data IOF a = GetChar (Char - a) | PutChar Char a | ...
with constructors for all elementary IO operations.
But how
On Thu, Aug 08, 2013 at 05:44:11PM +0100, Tom Ellis wrote:
On Thu, Aug 08, 2013 at 06:25:12PM +0200, Daniel Trstenjak wrote:
See [1] for an explanation of free monads in general. For IO in
particular,
define a functor
data IOF a = GetChar (Char - a) | PutChar Char
On Fri, Aug 09, 2013 at 12:38:45AM +0700, Kim-Ee Yeoh wrote:
On Thu, Aug 8, 2013 at 11:05 PM, Tom Ellis
tom-lists-haskell-cafe-2...@jaguarpaw.co.uk wrote:
On Thu, Aug 08, 2013 at 03:38:41PM +0200, Jerzy Karczmarczuk wrote:
One could simply implement IO as a free monad
Interesting. I
On Fri, Aug 09, 2013 at 12:53:56PM +0200, Gergely Risko wrote:
In the last 2-3 weeks I've been working on Haskell indentation inside
Emacs. I had some annoyances for a long time and fixed some of them.
The new mode is called hi2, it's heavily based on the current
haskell-indentation (part
On Fri, Aug 16, 2013 at 10:26:42AM -0400, Brandon Allbery wrote:
My understanding is that there's a rework of Arrow in progress that may
change this in the future, since *theoretical* Arrows are more distinct,
flexible and useful than the current implementation.
I'd like to know more about
On Sat, Aug 17, 2013 at 11:11:07AM +0200, Christopher Done wrote:
Anyone ever needed this? Me and John Wiegley were discussing a decent
name for it, John suggested inv as in involution. E.g.
inv reverse (take 10)
inv reverse (dropWhile isDigit)
trim = inv reverse (dropWhile isSpace) .
On Sat, Aug 17, 2013 at 11:59:24PM +0200, Hartmut Pfarr wrote:
{-# LANGUAGE OverloadedStrings #-}
import Database.PostgreSQL.Simple
import Database.PostgreSQL.Simple.FromRow
hello :: (FromRow a) = IO [a]
hello = do
conn - connect defaultConnectInfo
query_ conn select 2 + 2
Either
On Sun, Aug 18, 2013 at 10:16:06PM +0200, Hartmut Pfarr wrote:
I played a bit with your suggestion, and it is running now :-)
But instead of IO [Int] I think we need IO [Only Int] because
of the 1-element-tupel problem?
Yes you're right. I had forgotten that postgresql-simple dealt with
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
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 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.
On Thu, Aug 22, 2013 at 12:51:24PM -0300, Thiago Negri wrote:
How hard would it be to lift strictness annotations to type-level? E.g.
instead of
f :: Int - Int
f !x = x + 1
write
f :: !Int - Int
f x = x + 1
which would have the same effect. At least it would be transparent to the
On Mon, Aug 26, 2013 at 12:05:14PM -0700, Bryan O'Sullivan wrote:
On Mon, Aug 26, 2013 at 1:46 AM, Niklas Hambüchen m...@nh2.me wrote:
This is because sequence is implemented as
sequence (m:ms) = do x - m
xs - sequence ms
return
As an addendum to the recent discussion, can anyone explain why main crashes
quickly with a stack overflow, whereas main' is happy to print Hi for ages
(eventually crashing due to an out of memory condition)?
bignum = 100 * 1000 * 1000
main = replicateM bignum (return ())
main' =
On Wed, Sep 04, 2013 at 10:21:37PM +0800, yi lu wrote:
I want to read a text file, and store it in a *String*. But readFile will
get *IO String*. I search with google and they tell me it is not
necessarily to do so. Can you explain to me why is this? Furthermore, How
to read a file and store
On Fri, Sep 06, 2013 at 05:04:12PM +0200, Johannes Emerich wrote:
Weirdly, however, infix notation can also be used for unary functions with
polymorphic types, as the following ghci session shows:
Prelude :t (`id` 1)
(`id` 1) :: Num a = (a - t) - t
Prelude (`id` 1) (\y - show y ++
On Wed, Sep 04, 2013 at 04:35:17PM +0100, Tom Ellis wrote:
As an addendum to the recent discussion, can anyone explain why main crashes
quickly with a stack overflow, whereas main' is happy to print Hi for ages
(eventually crashing due to an out of memory condition)?
bignum = 100 * 1000
On Thu, Sep 12, 2013 at 09:21:20AM -0400, Scott Lawrence wrote:
Something's always bothered me about map and zipWith for ByteString. Why is it
map :: (Word8 - Word8) - ByteString - ByteString
but
zipWith :: (Word8 - Word8 - a) - ByteString - ByteString - [a]
Well, what if you
On Fri, Sep 20, 2013 at 06:34:04PM +0200, Stijn van Drongelen wrote:
Please find yourself a copy of What Every Computer Scientist Should Know
About Floating-Point Arithmetic by David Goldberg, and read it. It should
be very enlightening. It explains a bit about how IEEE754, pretty much the
On Fri, Sep 20, 2013 at 09:47:24PM +0530, damodar kulkarni wrote:
Ok, let's say it is the effect of truncation. But then how do you explain
this?
Prelude sqrt 10.0 == 3.1622776601683795
True
Prelude sqrt 10.0 == 3.1622776601683796
True
Here, the last digit **within the same precision
Does anyone recognise these typeclasses:
import Data.Profunctor (Profunctor)
import Data.Functor.Contravariant (Contravariant)
class Profunctor p = ProductProfunctor p where
empty :: p () ()
(***!) :: p a b - p a' b' - p (a, a') (b, b')
class Contravariant f =
On Tue, Oct 01, 2013 at 09:29:00AM +0200, Niklas Haas wrote:
On Tue, 1 Oct 2013 02:21:13 -0500, John Lato jwl...@gmail.com wrote:
It's not a solution per se, but it seems to me that there's no need for the
Monad superclass constraint on MonadIO. If that were removed, we could
just have
On Tue, Oct 01, 2013 at 12:11:23PM +0300, Roman Cheplyaka wrote:
Shouldn't it be an *Applicative* constraint?
class Applicative t = ApplicativeIO t where
liftIO :: IO a - t a
and require that
liftIO (pure x) = pure x
liftIO (f * x) = liftIO f * liftIO x
On Tue, Oct 01, 2013 at 03:17:40PM +0300, Yitzchak Gale wrote:
Tom Ellis wrote:
Shouldn't it be an *Applicative* constraint?
class Applicative t = ApplicativeIO t where
liftIO :: IO a - t a
and require that
liftIO (pure x) = pure x
liftIO (f * x) = liftIO f
On Wed, Oct 02, 2013 at 11:24:39AM +0200, Heinrich Apfelmus wrote:
I'm not sure whether the Eq instance you mention is actually
incorrect. I had always understood that Eq denotes an equivalence
relation, not necessarily equality on the constructor level.
There's a difference between
On Wed, Oct 02, 2013 at 03:46:42PM +0200, Stijn van Drongelen wrote:
* Operators in Eq and Ord diverge iff any of their parameters are bottom.
What's the benefit of this requirement, as opposed to, for example
False = _ = True
...
Tom
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