Hello,
while we are talking about strange semantic inequalities in the presence
of `seq` (supposed monads not satisfying the monad laws anymore...), I
just wanted to reiterate a point I made in a previous post, namely that
`seq` also makes the foldr/build-rule of shortcut deforestation [1]
wrong.
Andre W B Furtado wrote:
> > [Haddock cannot find perl]
> This works for me, but I'm not a Cygwin/Windows expert so I'm not sure
> what the canonical answer should be. On my system I have the Cygwin
> perl.exe in /cygwin/bin, and this is also /bin under cygwin, because by
> default Cygwin seems t
On Tue, 14 May 2002, Ken Shan wrote:
> On 2002-05-14T12:32:30-0400, Jan-Willem Maessen wrote:
> > And I'd really much rather we cleaned up the semantics of
> > seq---or better yet, fixed the problems with lazy evaluation which
> > make seq necessary in the first place.
>
> A general question: Wh
>
> However, it appears that the only place (short of Ericsson) I can actually
> work on a complex functional system is in academia. Unfortunately, this is
> not an option, as I have no Ph.D., and going back to school is probably not
> realistic.
There are other companies using Erlang, if not on
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G'day all.
On Tue, May 14, 2002 at 04:47:13PM -0500, Jeffrey Palmer wrote:
> Are there any options for people like me, or does my functional experience
> remain limited to the hobby* work I can squeeze in at night and on weekends?
>
> Thoughts?
The first thing you have to understand is that t
Hal Daume <[EMAIL PROTECTED]> writes:
> [seq is] useful for:
>
> debug :: Show a => a -> a
> debug x = unsafePerformIO (hPutStrLn stderr (show x)) `seq` x
>
> (Presumably "trace" is defined similarly)
>
> One may ask the question: what is seq useful for not in conjunction with
> unsafePerformI
True, but using seq you can define deepSeq/rnf (depening on which camp
you're from), which isn't misleading in this way.
--
Hal Daume III
"Computer science is no more about computers| [EMAIL PROTECTED]
than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume
On Tue, 14 May 20
hello,
this is misleading. seq only evaluates to whnf, i.e.
the outermost lazy constructor (or lambda) and that only if the
"seq ..." expression is actually evaluated, which is often tricky to
ensure. furthermore, for non-functions one can get the same behaviour,
by using a case with a pattern.
Hello all,
I've got a not-quite-so-technically-detailed question for everyone.
For the past ten or so years, I've been building relatively large "real-world"
software systems, and I've always been interested in finding new and
innovative ways to reduce complexity and improve system maintainabi
> One may ask the question: what is seq useful for not in conjunction with
> unsafePerformIO, other than efficiency. That, I don't know the answer to.
Here is an example.
> main::IO()
> main=do
> time1 <- getCPUTime
> w <- return $! calcSomething
> time2 <- getCPUTime
...
J
It's useful for:
debug :: Show a => a -> a
debug x = unsafePerformIO (hPutStrLn stderr (show x)) `seq` x
(Presumably "trace" is defined similarly)
One may ask the question: what is seq useful for not in conjunction with
unsafePerformIO, other than efficiency. That, I don't know the answer to.
On 2002-05-14T12:32:30-0400, Jan-Willem Maessen wrote:
> And I'd really much rather we cleaned up the semantics of
> seq---or better yet, fixed the problems with lazy evaluation which
> make seq necessary in the first place.
A general question: What is seq useful for, other than efficiency?
--
> "S.M.Kahrs" wrote:
> [snip]
> > I don't think this really solves the problem with the left unit
> > (not in general, and not for IO either),
> > it merely pushes it to a different place.
> [snip]
> Not being a category theorist I find this all a bit confusing.
Nothing to do with category theory
I've seen 'error "foo"' or simply 'undefined' used as a placeholder for
elements in a structure which we, as programmers, know will be filled in
soon. Often this makes the code clearer because the creation of the data
structure and filling in its values is separated (you could argue with
this, bu
"S.M.Kahrs" wrote:
[snip]
> I don't think this really solves the problem with the left unit
> (not in general, and not for IO either),
> it merely pushes it to a different place.
[snip]
Not being a category theorist I find this all a bit confusing. Can you
give an example where with GHC and the f
Robert Ennals <[EMAIL PROTECTED]> wrote:
> Surely that problem only arises if one insists on encoding all the relevant
> information inside a string.
This is pretty much the only option, because translators
and programmers are different people. Translators can deal with
simple text files with on
Dylan Thurston <[EMAIL PROTECTED]> writes:
> I don't think this is necessarily wise to drop this from the report
> altogether. To me, it seems comparable to associativity of addition
> for instances of Num; many instances don't satisfy it (e.g., Float),
> but it's a useful guideline to keep in mi
George Russel wrote:
[snip]
> I presume it would not in fact be difficult to synthesise a left identity at
> the cost of making things slower, thus (forgive any syntax errors, I'm not going to
> test this).
>
> data MonadIO a = Action (IO a) | Return a
> instance Monad (MonadIO a) where
>retu
> Robert Ennals <[EMAIL PROTECTED]> wrote:
> > I personally much prefer the syntax currently used in Haskell, which is also
> > essentially what is used in most other recent languages, including Java, C++,
> > and (god help me) Perl.
> >
> > In the example given, I could write:
> >
> > "I have
Dylan Thurston wrote:
[snip]
> I've often been bothered by the inconsistent treatment of laws in the
> report; why are there laws for functors, monads, and quot/rem and
> div/mod, and not much else? I'm pleased to see that the laws that are
> given actually do have exceptions.
[snip]
Even the quo
Robert Ennals <[EMAIL PROTECTED]> wrote:
> I personally much prefer the syntax currently used in Haskell, which is also
> essentially what is used in most other recent languages, including Java, C++,
> and (god help me) Perl.
>
> In the example given, I could write:
>
> "I have " ++ action ++
On Tue, May 14, 2002 at 04:57:12PM +0200, George Russell wrote:
> According to the report
> > Instances of Monad should satisfy the following laws:
> >
> >return a >>= k = k
> >m >>= return= m
> >m >>= (\x -> k x >>= h) = (m >>= k) >>= h
> so neither IO nor my even
On Tue, May 14, 2002 at 03:45:36PM +0100, Robert Ennals wrote:
> Just thought I would jump in and say that, unlike (it seems)
> everyone else, I hate printf in C. It is a horrible horrible
> inextensible hack of a function that I find extremely awkward to
> use.
> ...
> I personally much prefer th
tis 2002-05-14 klockan 16.45 skrev Robert Ennals:
> > Martin Norbäck <[EMAIL PROTECTED]> wrote:
> > > I agree that i18n needs positional arguments.
> > > What's wrong with simply doing like this:
> > >
> > > printf "I have %. %. %.."["trained", show 1, "Jedi"]
> > > printf "%2. %3. %1. I have
Simon Marlow wrote
[snip]
> So the IO monad in Haskell, at least as we understand it, doesn't
> satisfy the monad laws (or, depending on your point of view, seq breaks
> the monad laws).
[snip]
Cheers Simon. One of the awkward things about the Haskell events I implemented
is that although I make
> Martin Norbäck <[EMAIL PROTECTED]> wrote:
> > I agree that i18n needs positional arguments.
> > What's wrong with simply doing like this:
> >
> > printf "I have %. %. %.."["trained", show 1, "Jedi"]
> > printf "%2. %3. %1. I have." ["trained", show 1, "Jedi"]
>
> Nothing is exceptionally w
Martin Norbäck <[EMAIL PROTECTED]> wrote:
> I agree that i18n needs positional arguments.
> What's wrong with simply doing like this:
>
> printf "I have %. %. %.."["trained", show 1, "Jedi"]
> printf "%2. %3. %1. I have." ["trained", show 1, "Jedi"]
Nothing is exceptionally wrong with it, ex
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On Tue, May 14, 2002 at 12:14:02PM +0100, Simon Marlow wrote:
> The question we were considering was whether the following should hold
> in the IO monad:
>
> (return () >>= \_ -> undefined) `seq` 42 == undefined
>
> [as implied by the left-identity monad law]
>
> This discrepancy applie
On Tue, May 14, 2002, Simon Marlow wrote:
> An interesting revelation just occurred to Simon P.J. and myself while
> wondering about issues to do with exceptions in the IO monad (see
> discussion on [EMAIL PROTECTED] if you're interested).
>
> The question we were considering was whether the foll
An interesting revelation just occurred to Simon P.J. and myself while
wondering about issues to do with exceptions in the IO monad (see
discussion on [EMAIL PROTECTED] if you're interested).
The question we were considering was whether the following should hold
in the IO monad:
(return
On Tuesday, May 14, 2002, at 06:37 AM, anatoli wrote:
> Brian Huffman <[EMAIL PROTECTED]> wrote:
>> Here is a printf-style function that I hacked up this morning; it uses
>> type
>> classes but it doesn't need functional dependencies:
> [snip]
>
> It's very nice and even extendable, though `cla
tis 2002-05-14 klockan 06.37 skrev anatoli:
> Brian Huffman <[EMAIL PROTECTED]> wrote:
> > Here is a printf-style function that I hacked up this morning; it uses type
> > classes but it doesn't need functional dependencies:
> [snip]
>
> It's very nice and even extendable, though `class Printf Str
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