Mark,
Whether a variable is bound or free depends on the scope under consideration. In
(\x. x) (\y. x)
the variable x is bound in \x. x, but free in \y. x; hence, it's free in (\x.
x) (\y. x) as a whole. However, in
\x. (\x. x) (\y. x)
it's bound...
HTH,
Stefan
__
Ok, after mulling over the issues that Will Ness has brought up in
the last few days [1], I think I have a partial explanation for the
apparent tension between Will's observations and Heinrich Apfelmus's
Implicit Heaps article [2], which both concern the implementation of
mergeAll [3].
The merg
On 01:08 Sun 05 Dec , Serguey Zefirov wrote:
> Why TypeRep does have equality and doesn't have ordering?
>
> It would be good to have that.
I think the problem is, that it's hard to give an ordering that stays the
same for all runs of your program. If you don't need this property you could
us
I started for cleaner diffs and easier editing - I can add/remove a
line at the end without editing any other line. Eventually I grew to
like the look of it.
Both styles are common, from what I can tell.
Antoine
On Wed, Dec 29, 2010 at 11:40 PM, Daryoush Mehrtash wrote:
> Why do people put ";
Hi,
doc:
http://www.haskell.org/ghc/docs/7.0-latest/html/libraries/base-4.3.0.0/Control-Concurrent-SampleVar.html
source:
http://www.haskell.org/ghc/docs/7.0-latest/html/libraries/base-4.3.0.0/src/Control-Concurrent-SampleVar.html
The documentation for Control.Concurrent.SampleVar implies tha
Why do people put ";" in do {}, or "," in data fields, at the beginning
of the line?
--
Daryoush
Weblog: http://onfp.blogspot.com/
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First, what type would such a function have?
Certainly not [a]->[b], because that type say that it can take a list of any
type and turn it into a list of any other type, e.g.,
[Int]->[Bool].
On Thu, Dec 30, 2010 at 4:05 AM, william murphy wrote:
> Hi All,
>
> I've spent a lot of time trying to w
> Note, that this will not run on Windows, as it gives command
> /usr/sbin/sendmail
It sounds like mime-mail may be getting native support soon, but until
then you may try what I've had success with on Windows.
Grab a sendmail replacement like the one at
http://glob.com.au/sendmail/. It's just
Hi all,
Thanks for your comments
Maybe I should clarify...
For example,
5.2 FREE:
If E1 = \y.xy then x is free
If E2 = \z.z then x is not even mentioned
So E = E1 E2 = x (\z.z) and x is free as expected
So E = E2 E1 = \y.xy and x is free as expected
5.3 BOUND:
=
If E1 = \x.xy
Hi,
You're looking for 'when' as in:
> do
> condition <- something
> when condition $ other things
> more things
http://hackage.haskell.org/packages/archive/base/latest/doc/html/Control-Monad.html#v:when
It is quite handy.
Take care,
Antoine
On Wed, Dec 29, 2010 at 10:14 PM, Magicloud Magi
On Wed, Dec 29, 2010 at 9:22 PM, Mark Spezzano wrote:
> Duh, Sorry. Yes, there was a typo
>
> the second one should read
>
> If E is a combination E1 E2 then X is bound in E if and only if X is bound
> in E1 or is bound in E2.
>
Seems odd. I recommend you always work from at least three differe
Duh, Sorry. Yes, there was a typo
the second one should read
If E is a combination E1 E2 then X is bound in E if and only if X is bound in
E1 or is bound in E2.
Apologies for that oversight!
Mark
On 30/12/2010, at 1:21 PM, Antoine Latter wrote:
> Was there a typo in your email? Because thos
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
On 12/29/10 22:05 , william murphy wrote:
> I've spent a lot of time trying to write a version of concat, which
> concatenates lists of any "depth":
> So:
> concat'' [[[1,2],[3,4]],[[5]]] would return: [1,2,3,4,5]
You can't do that, at l
Hi,
In Haskell's way, normally, we write:
if condition then
expression_true
else
expression_false
But I just heard that, in fancy way, we could do:
do
ifNeedToDo >> doIt
bluh
May I have any clue here?
--
竹密岂妨流水过
山高哪阻野云飞
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On Wed, Dec 29, 2010 at 7:22 PM, aditya siram wrote:
> My brain turns into strange braid when I see this kind of thing. I
> don't quite understand it and I've never used it in real world code
> but I'll try and explain anyway. Caveat emptor.
>
Once when I was parsing a group of source files into
Hi All,
I've spent a lot of time trying to write a version of concat, which
concatenates lists of any "depth":
So:
concat'' [[[1,2],[3,4]],[[5]]] would return: [1,2,3,4,5]
The code is:
concat'' :: [a] -> [b]
concat'' ((y:ys):xs) = (concat'' (y:ys)) ++ (concat'' xs)
concat'' []
Was there a typo in your email? Because those two definitions appear
identical. I could be missing something - I haven't read that book.
Antoine
On Wed, Dec 29, 2010 at 9:05 PM, Mark Spezzano
wrote:
> Hi,
>
> Presently I am going through AJT Davie's text "An Introduction to Functional
> Program
Hi,
Presently I am going through AJT Davie's text "An Introduction to Functional
Programming Systems Using Haskell".
On page 84, regarding formal definitions of FREE and BOUND variables he gives
Defn 5.2 as
The variable X is free in the expression E in the following cases
a)
b) If E is a c
Check out the "Time Profiling" of the Chapter 25 of Real World Haskell
[1] for a detailed explanation.
-deech
[1] http://book.realworldhaskell.org/read/profiling-and-optimization.html
On Wed, Dec 29, 2010 at 6:48 PM, Aaron Gray wrote:
> What are these comments for in Happy ?
> {-# SCC "Mangl
What are these comments for in Happy ?
{-# SCC "Mangler" #-}
Many thanks in advance,
Aaron
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Hi all,
Manatee-0.1.6 release, sorry for late, I was tired of the many trivial this
month.
http://www.youtube.com/watch?v=weS6zys3U8k
hackage.haskell.org/package/manatee
New version Manatee support customize and hot-swap, like elisp for Emacs, but
much much fast and
safe.
Please look ht
2010/12/30 David Leimbach :
>
> Reader Writer State is commonly needed in big applications so transformers
> provides one for us:
> http://hackage.haskell.org/packages/archive/transformers/0.2.2.0/doc/html/Control-Monad-Trans-RWS-Lazy.html
> Pretty cool stuff if you ask me. I often wondered about
On Wed, Dec 29, 2010 at 1:48 PM, Michael Lazarev
wrote:
> 2010/12/29 michael rice
> > I had an "Aha!" moment and it all makes sense now. Just as the State
> monad can hold a generator (which can change) and pass it down a calculation
> chain, a Reader monad can hold an environment (which doesn't
Indeed, one might think that there is very little new :)
I also recommend the following handy book on functional programming (based
on Landin's ideas among others ) by William H Burge called recursive
Programming Techniques from 1975.
http://www.amazon.com/gp/product/0201144506?SubscriptionId=0QC
2010/12/29 michael rice
> I had an "Aha!" moment and it all makes sense now. Just as the State monad
> can hold a generator (which can change) and pass it down a calculation chain,
> a Reader monad can hold an environment (which doesn't change) and pass it
> down a calculation chain. I was wond
2010/12/29 Albert Y. C. Lai
> On 10-12-29 12:50 PM, michael rice wrote:
>
>> I think of (r -> m a) as a type signature and Int or Bool by themselves
>> as types. So, all type signatures are themselves types?
>>
>
> http://www.haskell.org/onlinereport/haskell2010/haskellch4.html#x10-620004
>
> In
On 10-12-29 12:50 PM, michael rice wrote:
I think of (r -> m a) as a type signature and Int or Bool by themselves
as types. So, all type signatures are themselves types?
http://www.haskell.org/onlinereport/haskell2010/haskellch4.html#x10-620004
In particular
gendecl → vars :: [context =>] typ
Hi, Daniel.
I had an "Aha!" moment and it all makes sense now. Just as the State monad can
hold a generator (which can change) and pass it down a calculation chain, a
Reader monad can hold an environment (which doesn't change) and pass it down a
calculation chain. I was wondering how I could in
On Wednesday 29 December 2010 19:30:11, michael rice wrote:
> Yes, I'd already noticed that ReaderT preceded Reader. Guess I'll have
> to check out the Indentity monad too. I hope it's not dependent upon yet
> another monad.
No, the Identity monad stands alone.
And as the name suggests, it's pret
On Wednesday 29 December 2010 15:41:22, Johannes Waldmann wrote:
> > ghci> (8000*2^20) `mod` (2^32)
> > 4093640704
> >
> > Seems GHC uses Word for the allocation figures
Looking at the rts-code, maxHeapSize is in blocks (4096 bytes, as far as I
can see) and the code for setting it uses double and
Hi, Michael.
Yes, I'd already noticed that ReaderT preceded Reader. Guess I'll have to check
out the Indentity monad too. I hope it's not dependent upon yet another monad.
;-)
Thanks for the link. I go there a lot.
Michael
--- On Wed, 12/29/10, Michael Lazarev wrote:
From: Michael Lazarev
Hi,
Michael Rice wrote:
I think of (r -> m a) as a type signature and Int or Bool by themselves
as types. So, all type signatures are themselves types?
Yes.
In Haskell, functions are first class, so function types like (r -> m a)
are themselves types.
Tillmann
__
I think of (r -> m a) as a type signature and Int or Bool by themselves as
types. So, all type signatures are themselves types?
Michael
--- On Wed, 12/29/10, Henning Thielemann wrote:
From: Henning Thielemann
Subject: Re: [Haskell-cafe] Reader monad
To: "michael rice"
Cc: haskell-cafe@haskel
2010/12/29 michael rice
>
> From the docs (and tuts) newtype creates a new type out of an existing
type
> and gives a single constructor for doing so.
>
> what is the existing type?
Michael, you may want to see this section:
http://learnyouahaskell.com/functors-applicative-functors-and-monoids#t
On Wed, 29 Dec 2010, michael rice wrote:
In the case of ReaderT and StateT
newtype ReaderT r m a = ReaderT {
-- | The underlying computation, as a function of the environment.
runReaderT :: r -> m a
}
newtype StateT s m a = StateT { runStateT :: s -> m (a, s) }
what is th
Hi, Ryan.
Since I'm trying to understand Reader, I wanted to be aware of all cases of
Reader.
==
>From the docs (and tuts) newtype creates a new type out of an existing type
and gives a single constructor for doing so.
From: http://www.haskell.org/tutorial/moretypes.html
newtype
On Wed, Dec 29, 2010 at 8:06 AM, michael rice wrote:
> Is there an unparameterizable reader monad?
I'm not sure this is the answer you are looking for, but it seems like the
obvious one.
Pick an "r", say "String". Now "Reader String" is an unparameterizable
reader monad that passes around a St
From: Control.Monad.Reader
type Reader r = ReaderT r IdentityThe parameterizable reader monad.
Computations are functions of a shared environment.
The return function ignores the environment, while >>= passes
the inherited environment to both subcomputations
Is there an unparameteri
On Wed, 29 Dec 2010, Robert Clausecker wrote:
Am Mittwoch, den 29.12.2010, 13:29 +0100 schrieb Henning Thielemann:
I don't know, I hope it's doing its best. :-) You might compare speed of
Array.accum with a manually written foldl with (//).
At a glance onto it's sourcecode it actually does,
> ghci> (8000*2^20) `mod` (2^32)
> 4093640704
>
> Seems GHC uses Word for the allocation figures
Interesting. Then how can I set the memory bounds that I want?
The machine has 12 GB, and if I leave out any RTS options,
then the ghc-compiled program will happily consume it all.
> and you have a
On Sun, 5 Dec 2010, Henning Thielemann wrote:
Thomas Schilling schrieb:
I created http://www.haskell.org/haskellwiki/MigratingWikiContent to
list known issues and workarounds. Please feel free to extend that
page where needed.
...
I did not like to add these items while having to log in ov
On Tue, 28 Dec 2010, aditya siram wrote:
The problem here is that unfortunately the Haskell type system cannot
do coercion.
I'd omit the "unfortunately". For me it is a good thing that Haskell does
not silently apply lossy number conversions, as e.g. MatLab does.
'realToFrac' allows conve
On Tuesday 28 December 2010 20:37:50, Johannes Waldmann wrote:
> Hello.
>
> When I run a program compiled with ghc-6.12.3 like this:
>
> ... +RTS -A2G -M8G -s
>
> I get as an answer:
>
> Heap exhausted;
> Current maximum heap size is 0 bytes (0 MB);
> use `+RTS -M' to increase it.
Overflow, I'm a
The unabated debate about exactly how much category theory one needs
to know to understand that strange beast of IO prompts a thought if
monads, like related continuations, are the things that are destined
to be rediscovered time and time again.
An old (1994) paper on category theory monads and f
Sure -- I'll look at doing that. No time today but should be able to
look at that on Friday.
-Rob
On Wed, Dec 29, 2010 at 6:02 AM, Michael Snoyman wrote:
> This looks very good, thank you! One comment: do you think it would be
> possible to add a function for sending a mime-mail Mail datatype
>
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