Floats don't like to be referenced [was: Buggy derived instance of Show]
Scary, but true...the floats in my version of ghc don't like to be referenced. The program data MassPnt = MassPnt Float (Float, Float) deriving (Show) main = do print 1.18088e+11-- (1) let x = 1.18088e+11 p = MassPnt x (-0.768153, -0.742202) -- (*) print x -- (2) prints `1.18088e+11' successfully at line (1), but fails in line (2) with `Fail: Char.intToDigit: not a digit'. But now the *interesting* part: When I remove the line (*), everything works just fine! Floats just don't like to be referenced...or is there not enough space allocated for them in the heap and they tend to be overwritten? Now, I don't have the lattest version of GHC, so maybe someone else hit that problem earlier (I also did't follow all discussions on this list). (As said earlier, I used ghc 2.05 on Linux 2.0.30.) Manuel P.S.: Of course, I think that the problem that I reported earlier was actually caused by the above one.
Still unhappy
Guess what? It's the old 'for i in ;' problem again. Try 'make install SHELL=bash' (I think the upper case is important). Yes, the upper case is important. However, installing happy from the binaries still does not work. Here is a summary of my undertakings: gunzip happy-1.5-sparc-sun-solaris2.tar.gz | tar -xf - mkdir fptools.sparc cd fptools.sparc lndir ../fptools . ./configure --prefix=$HOME/FP/ghc creating ./config.status creating Makefile ** Configuration done, ready to either 'make install' or 'make in-place'. (see README and INSTALL files for more info.) ** gold 958 make install SHELL=bash Configuring happy, version 1.5, on sparc-sun-solaris2 ... rehash happy /home/III/a/ralf/FP/ghc/bin/happy: /home/III/a/ralf/FP/ghc/lib/happy-1.5/happy.bin: not found Any suggestions, Ralf
Re: Strange module exportation behavior
Conal: great bug report; thanks. Meanwhile a workaround is to use qualified names in the export list for Test2: module Test2( Test1.foo, module Test2 ) import Test1 hiding(main) main = ... Inconvenient, but it should get you rolling. Simon, Sigbjorn: I've fixed this and checked in the changes (in rename/..). Conal will need a new build in due course. Simon I'm getting strange behavior from both GHC and Hugs w.r.t. module exportations. They disagree with each other somewhat and both seem wrong, although I'm not certain I understand the report on this matter. Here are two test programs. First Test1.hs: module Test1 (module Test1) where main = putStrLn "Test1's main" foo = "Test1 foo" In Test2.hs, I want to modify and extend Test1, keeping "foo" but replacing main. module Test2 (module Test1, module Test2) where import Test1 hiding (main) main = putStrLn "Test2's main" bar = foo ++ " plus Test2 bar"
Re: error: (misc)
Alex Ferguson writes: install-sh does a fine line in unhelpful error messages: well, error message singular, at any rate... for i in hp2ps; do \ /export/home/ferguson/ghc-3.00/build/install-sh -c -g ghc-admin -s $i /usr/local/bin; \ done hp2ps:error reading file This seems to be its catch-all for anything that goes wrong, making diagnosis a tad tricky. On one machine it was a full disk, another one I'm still trying to puzzle out... install-sh is the fallback script used if the configure script is unable to find an OK looking `install' somewhere along your PATH. If install-sh is such a pain to work with, you may want to try out the `install' that comes with the GNU fileutils. --Sigbjorn
Re: Fun with 3.00
One can play funny games with GHC-3.00 and the following program
(a small fragment of a Happy-generated parser):
--
module Foo ( happyParse ) where
action_0 1 = \j tk _ - action_1 j j tk (HappyState action_1)
action_1 3 = error "Bar"
action_1 _ = \i tk st@(HappyState action) sts stk - action (-1) (-1) tk st sts
(Just i : stk)
happyParse = action_0 2 2 '-' (HappyState action_0) [] [] 2
newtype HappyState b c =
HappyState (Int - Int - b - HappyState b c - [HappyState b c] - c)
--
Great program! Thanks for isolating it.
Simon: pls add to regression suite
There are two problems. One is a long-standing bit of grubbiness
in the code generator; hence fun_result_ty panic. I've fixed that
(still grubbily, I fear).
GHC goes into a loop in the update analyser. Reason: the
recursive contravariance of HappyState. Consider:
action_1 j j tk (HappyState action_1) sts stk
= {unfold action_1}
action_1 (-1) (-1) tk (HappyState action_1) sts (Just j:stk)
= {unfold action_1 again}
...
Neither action_0 nor action_1 is recursive, but infinite unfolding
can still occur. This can cause the simplifier to loop, though
on this occasion it doesn't, but only because action_1 is
considered too big to unfold. But it does make the update analyser
loop, for some obscure reason. It wouldn't surprise me if the
strictness analyser looped too, but it doesn't.
For some reason there's no flag to switch off the update analyser.
It does very little good anyway, so just switch it off by force
in ghc/driver/ghc.lprl (look for -fupdate-anal).
I've known about the possibility of looping in the simpifier for some time, but
never seen it in a real program. I have no idea how to spot it in a clean way,
and without disabling lots of useful inlining. (I prevent looping mainly by
treating letrec carefully.) Ideas welcome
Simon
Fun with 3.00
One can play funny games with GHC-3.00 and the following program
(a small fragment of a Happy-generated parser):
--
module Foo ( happyParse ) where
action_0 1 = \j tk _ - action_1 j j tk (HappyState action_1)
action_1 3 = error "Bar"
action_1 _ = \i tk st@(HappyState action) sts stk - action (-1) (-1) tk st sts (Just
i : stk)
happyParse = action_0 2 2 '-' (HappyState action_0) [] [] 2
newtype HappyState b c =
HappyState (Int - Int - b - HappyState b c - [HappyState b c] - c)
--
* Compiling it as-is with "ghc-3.00 -O -c Foo.hs" yields:
= panic! (the `impossible' happened):
fun_result_ty: 6 PrelBase.Int{-3f-}
- PrelBase.Int{-3f-}
- b_tr74
- Foo.HappyState{-r6P-} b_tr74 c_tr75
- [Foo.HappyState{-r6P-} b_tr74 c_tr75]
- c_tr75
Please report it as a compiler bug to [EMAIL PROTECTED]
* If newtype is changed to data or "( happyParse )" is deleted,
it compiles fine.
* GHC-2.10 doesn't complain in any way.
* If the first equation of action_1 is commented out, GHC seems to loop:
ghc-3.00 -O -c Foo.hs -H50M -K50M
= GHC's heap exhausted;
while trying to allocate 20 bytes in a 5000-byte heap;
use the `-Hsize' option to increase the total heap size.
Cheers,
Sven "Unhappy-too" Panne
--
Sven PanneTel.: +49/89/2178-2235
LMU, Institut fuer Informatik FAX : +49/89/2178-2211
LFE Programmier- und Modellierungssprachen Oettingenstr. 67
mailto:[EMAIL PROTECTED]D-80538 Muenchen
http://www.pms.informatik.uni-muenchen.de/mitarbeiter/panne
Re: haskell and exceptions
Matthias Fischmann writes ... I am now trying to learn Haskell for half a week and I like it a lot. But I still did not find out too much about exception handling. Is it possible that there is no ml-like mechanism with `raise' and `handle' built in? Yes, I know about types like data Result t = ERROR | Yes t and I also read the chapter in the report about IO, monads, and userError. But this seems all a little clumsy compared to the elegant and simple exceptions in standard ml or even ugly languages like java. Did I miss the point? Are there exceptions libraries? Is there any extension to Haskell in some existent implementation that handles my needs? How do you handle exceptions in your Haskell programs? No, there are no extensions for handling exceptions. Some may think that this is a bug but I think it's a feature ;-). First of all it's against Haskell's spirit of being a pure functional language. Consider raise First + raise Second handle First = 1 | Second = 2, what is the value of this expression? It clearly depends on the order of evaluation. SML defines this rigorously (right?). However, Haskell is a lazy language, so even if the language designers would undergo the task of defining the evaluation order, this is nothing which is easy for the user to understand. I usually try to avoid partial functions. That's easier as one might suppose at first (if one is willing to invent new data types). Consider operations on priority queues. data OptPair a b = Null | Pair a b class PriorityQueue q where empty :: (Ord a) = q a meld :: (Ord a) = q a - q a - q a splitMin :: (Ord a) = q a - OptPair a (q a) Instead of defining `getMin' and `deleteMin' which are both partial functions we define `splitMin' which combines both. Here is a simple application of `splitMin'. toOrderedList q = case splitMin q of Null - [] Pair a q - a : toOrderedList q For error reporting and alike I usually use an exception monad. Hope this helps, Ralf
Re: haskell and exceptions
On Thu, 29 Jan 1998, Ralf Hinze wrote:
Matthias Fischmann writes ...
I am now trying to learn Haskell for half a week and I like it a lot.
But I still did not find out too much about exception handling. Is it
possible that there is no ml-like mechanism with `raise' and `handle'
built in? Yes, I know about types like
data Result t = ERROR | Yes t
and I also read the chapter in the report about IO, monads, and
userError. But this seems all a little clumsy compared to the elegant
and simple exceptions in standard ml or even ugly languages like java.
Did I miss the point? Are there exceptions libraries? Is there any
extension to Haskell in some existent implementation that handles my
needs? How do you handle exceptions in your Haskell programs?
No, there are no extensions for handling exceptions. Some may think
that this is a bug but I think it's a feature ;-). First of all it's
against Haskell's spirit of being a pure functional language. Consider
raise First + raise Second handle First = 1 | Second = 2,
what is the value of this expression? It clearly depends on the order
of evaluation. SML defines this rigorously (right?). However, Haskell
is a lazy language, so even if the language designers would undergo
the task of defining the evaluation order, this is nothing which is
easy for the user to understand.
Don't even more extreme problems with exceptions arise because of lazy io?
E.g., if a function produces a list of integers but can produce an
exception after calculating some of the first elements of the list (say
divide by zero or something), then if this function is used by a lazy
output function (say putStr),
then by the time the exception gets thrown all the elements already
produced will already have been sent to the screen and this can't be
rescinded.
E.g., using the hugs interpreter,
Prelude putStr(show [1/2,2/3,4/0])
[0.5, 0.67,
Program error: {primDivDouble 4.0 0.0}
(Imagine that program error was actually an exception that would be caught
somewhere else.)
In ML the strictness of the language means that this won't happen, and
because it's a functional language there's a guarantee that there are no
`program variables' being corrupted. I'd presume imperative languages like
C++ and java require much more careful, generalised exception planning. (I
don't use C++ exceptions in my programming :-) )
cheers, dave
-
email reply: [EMAIL PROTECTED] "Life is good for only two things,
http://www.cs.bris.ac.uk/~tweed/discovering mathematics and teaching
work tel: (0117) 9545104mathematics" -- Simeon Poisson
application announce
Announcement: The Algebraic Domain Constructor DoCon, version 1.06 --- DoCon-1.06 a computer algebra program written in a pure functional language Haskell (version 1.4) can be copied freely, as a source program (see license.txt) from ftp.botik.ru:/pub/local/Mechveliani/docon/1.06/ -- Abilities (mostly, commutative algebra): Mathematical library: - Linear algebra over a Euclidean domain: reduction to the staircase and diagonal forms of matrix, solving a system, - Polynomial arithmetic in R[x1,...,xn], R a commutative ring, - g.c.d in R[x1,...,xn], R a factorial ring, - Factorization for the univariate polynomial over a finite field, - Groebner basis and syzygy generators in a free module over R[x1,...,xn], R a Euclidean ring; - Symmetric function package; Category hierarchy: - (static) Set, Semigroup, Group, Ring, SyzygySolvableRing, and so on, - dynamic Subset, Subgroup, Subring, Ideal, ... operations; Functors of the - Direct product of the Sets, (semi)Groups, Rings, - Matrix algebra over a commutative ring, - Polynomial algebra over a commutative ring, - Fraction field for a factorial ring, - Residue ring; Property processing: - the evaluation of certain small set of the most important algebraic property values is supported, such as Finite, IsCyclicGroup, IsMaximalIdeal, etc. -- For the Haskell language materials, see http://haskell.org DoCon-1.06 is a package of the Haskell programs. It needs theGlasgow Haskell system ghc-2.10 - or any higher compatible version - for DoCon to be built from the sources and exploited. ghc is also freely available with its sources: ftp.dcs.gla.ac.uk/pub/haskell/glasgow/ src.doc.ic.ac.uk/pub/computing/programming/languages/haskell/ glasgow/ -- DoCon differs from the most CA programs in that it enables the programmer to set the algorithms in the natural and generic mathe- matical form. It uses the categorial approach to the algebraic computation - like the wide-known AXIOM system (AXIOM is a trademark of the Numerical Algorithms Group Ltd) - though DoCon has a smaller library of algorithms. DoCon is pure functional, contains no side effects, and is written in Haskell only. To use DoCon-1.06 means to write the programs in Haskell, compile and link them under ghc importing object and interface modules from DoCon-1.06 export directory. Documentation: everything is explained in manual.txt -- Platforms: - DoCon-1.06 has to work everywhere where ghc-2.10 works (lots of platforms). Though, we have seen it working only on linux-i386-unknown. We hope it will install, as it is, on any Unix machine. And we doubt about Windows (if only there exists ghc-2.10 for Windows) - the question concerns only the installation Makefile. Probably, it would not be difficult to port DoCon to other Haskell implementations: Yale, Chalmers, Hugs, and so on. And we will be grateful to the users that make DoCon ports to various compilers and environments. Plans: -- the future DoCon versions have to implement more of mathematics, use the extended language tools, as the multiple parameter categories and others. Also the contributions are welcome. The known *bugs* and their walk-arounds are listed in ftp.botik.ru:/pub/local/Mechveliani/docon/1.06/bugs.txt The remarks are welcome: [EMAIL PROTECTED] Sergey D.Mechveliani senior researcher, Program Systems Institute, 152140, Pereslavl-Zalessky, Russia. e-mail [EMAIL PROTECTED] phone +7(08535)98022
