I am playing around with KiCS and I have a strange problem, when I
evaluate a goal the variable bindings are not displayed, I see only
the value of the expression.
The idea is, that you decide yourself which bindings you want to see.
For example, you write (let x free in (not x,x)) to get
Hi folks,
I am trying to integrate my own preprocessor into a cabal build
process. But there are several points that I get stuck with. Could
someone help me, please?
A simplification of my problem:
I have files Abc.foo and each of them should be transformed into
Abc.hs by calling
Sometimes the synchronicity of events is eery. Incidentally I have
just written a proposal for just such a project.
You can have a look at it at
http://www-ps.informatik.uni-kiel.de/~bbr/WebOfProofs.html
Although not directly mentioned in the proposal, there will be a lot
of Converting
Hi folks,
I have been surprised by the derived instances of Data/Typeable when
using the combinator ext1Q. First look at the following definition:
useExt1 :: Data a = a - ()
useExt1 = undefined `ext1Q` (\ (Just _) - ())
testExt1 :: ()
testExt1 = useExt1 (Just ())
As I expected, testExt1
José Pedro Magalhães wrote:
Hi Bernd,
I guess this might be the same issue reported some time ago (
http://thread.gmane.org/gmane.comp.lang.haskell.generics/53/focus=54): the
derived instances of Data do not define dataCast1. If you define your own
instance of Data for MyMaybe and add the
I think it would be nice to have some speedy optimizations turned on by
default in ghc. Might even be good to win new users.
But I also think that much hacking for and around ghc+tool support needs
a way to achieve what -O0 does today.
So, how about an -O(-1) or flag?
I suspect that if all modules are compiled -O0, then you recompile one
module with -O2, high up in the dependency graph (i.e. it depends on
many lower-level modules), plus all things that in turn depend on it
(--make), you will not get the good performance you expect. None of the
lower-level
Don Stewart wrote:
You almost always want to profile with full optimisations on.
Otherwise its not even close to measuring the kind of code you're
actually running.
Ian Lynagh wrote:
This should work, for the reasons that you give. Did you use options
like +RTS -p when running the program?
Hi all,
I have noticed that there is a great difference between optimizing
modules separately and all at once, e.g., with -fforce-recomp. I have
had examples factors up to 15 in run time (and even different behavior
in context with unsafePerformIO).
Is there any option that makes ghc write out
Simon Peyton-Jones wrote:
GHC does a lot of cross-module inlining already, and *does* write stuff into
interface files, provided you use -O.
I used -O4. Is that the bad thing?
I'm always interested in performance differences of a factor of 15 though!
Can you supply an example (as small
Sorry to ask a C question here, but I could not find an answer on the net.
How do I create a library that can be used in ghci?
This is the situation:
I have a c file coracle.c. I do
/tmp$ cc -c -o coracle.o coracle.c
/tmp$ ar rc libcoracle.a coracle.o
/tmp$ ranlib libcoracle.a
and then I the
Simon Marlow wrote:
Perhaps there are some trivial examples of
unshared thunks that we could spot, though.
The sharing analysis in the interpreter is also very simple and
inexpensive. But the gain is frequent. Maybe giving it a try would be
worthwhile.
Thanks again for all your answers!
Bernd
Simon Marlow wrote:
Normally it's done like this:
$ gcc -fPIC -c foo.c
$ gcc -shared -o libfoo.so foo.o
Hope this helps.
Right away! Big Thanks!
Bernd
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Simon Peyton-Jones wrote:
Any chance of documenting your experience on the GHC user documentation page?
http://haskell.org/haskellwiki/GHC (under collaborative
documentation)
A kind of how-to that worked for you, with pointers to relevant manual parts
etc.
Simon
Is this
I have got around the problem by defining my unsafe actions by the
foreign function interface. But I still think there is a bug concerning
stack use in unsafePerformIO in ghc. And I also think that this bug
potentially concerns every use of unsafe. Or did I just not get the
point of your argument
Simon Marlow wrote:
So the upshot is: you can use unsafeDupablePerformIO right now, or you
can wait until I've tested and committed this patch to get
tail-recursion with unsafePerformIO.
Wow, thank you for the detailed answer! That was really interesting.
I've no idea how it works in Hugs,
There is another point that makes me wonder now. If the update frame for
the recursive call is the problem then my solution with foreign C
functions would produce a bad stack also. But this is not the case.
The code looks now like this:
sim [] = True
sim (_:xs) = yags (sim xs)
ref =
Thanks for your answer Simon.
Simon Marlow wrote:
Bernd Brassel wrote:
Consider the following program:
module Stack where
import System.IO.Unsafe
main = print (sim (replicate 1299959 ()))
sim [] = True
sim (_:xs) = goodStack (sim xs)
goodStack x = fromJust (Just x
Consider the following program:
module Stack where
import System.IO.Unsafe
main = print (sim (replicate 1299959 ()))
sim [] = True
sim (_:xs) = goodStack (sim xs)
goodStack x = fromJust (Just x) --no stack overflow
badStack x = unsafePerformIO (return x) --stack overflow
The following program reveals a performance bug in ghc 6.6
module HCBenchmark where
type M1 a = ()
type M2 a = M1 a
type M3 a = M2 a
type M4 a = M3 a
type M5 a = M4 a
type M a = M4 a -- use M5 for 10 times the compile time and M3 for 1/10
f :: M (M (M (M (M (M (M (M (M (M x)
f = ()
Simon Peyton-Jones schrieb:
It's a perf bug in 6.6, happily fixed in 6.8.1
Great news! Thank you!
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Is it already a known problem that the preprocessor cannot cope with the
whole set of possible string declarations?
$ cat long1.hs
{-# OPTIONS -cpp #-}
s = abc\
\defg
main = putStrLn s
$ ghc long1.hs
long1.hs:3:14:
lexical error in string/character literal at character 'e'
$ cat
Hello to all who have given me hints an suggestions about this topic
whether directly by mail or over the mailing list. I do now have a much
more concrete idea of how to optimize my programs.
Thanks for your time!
Bernd
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Hi Stefan!
Thanks for your answer.
Stefan O'Rear wrote:
Might I suggest, that the problem is your use of unsafePerformIO?
Yes you might. And you are surely right. But not using it in this way is
not an alternative.
why do you want to do this unsafely,
instead of just using 'length'?
Hi David,
thank you! This is really useful information!
I think it's the let floating (out) together with common subexpression
elimination:
ghc --make -O2 -no-recomp -fno-cse -o curry-no-cse curry.hs
[1 of 1] Compiling Main ( curry.hs, curry.o )
Linking curry-no-cse ...
May I suggest a third route that has the advantages of both your
approaches. The backside is of course that it takes a bit of work. My
suggestion is to do an effect analysis of your curry programs to
identify the purely functional parts and compile them directly to pure
Haskell. The rest of
I think you'll find it useful to be explicit about what you are relying on.
Yes, good point.
For example I think that if your program contains two calls
unsafePerformIO e1
unsafePerformIO e2
then
* You don't care about the *order* in which these are performed
Right, the
Hi Neil, hi Don!
Nice meeting you at ICFP by the way.
Can you give a specific example of what you have tried to do, and how it
failed?
I have attached a short synopsis of what our Curry to Haskell
conceptually does. I could explain what all the parts mean and why they
are defined this way, if
Neil Mitchell schrieb:
It varies by each piece of code, can you post a code fragment that
gets optimised in the wrong way?
Sorry for posting this twice! I have added the code to the other thread.
Thanks!
Bernd
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time to invoke the no-inline pragmata, but they seem to have no
effect at all. Recently at ICFP, Neil Mitchell told me that there
definitely is a way to avoid this problem. But does anybody know how?
Thanks for your help!
Bernd Brassel
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I am a bit confused by GHC behaviour for the following variants of a
program:
data A = A (Int - A)
f = A g
g _ = f
h = g 'c'
ghc:
Error:
Couldn't match `Int' against `Char'
The problem is that a small change ommits the error:
data A = A (Int - A)
f = A g
where
g _ = f
h = g 'c'
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