Dear all,
I was playing around with GADT-records again and ran into behaviour that
I'm not sure is intentional. Given this program:
{-#LANGUAGE GADTs #-}
data FooBar x a where
Foo :: { fooBar :: a } - FooBar Char a
Bar :: { fooBar :: a } - FooBar Bool a
GHC tells me this:
Erratum; Of course, I meant that I had expected the different
occurrences of 'x' to have the same uniques. Similarly, the different
occurrences of 'y'. I did *not* expect 'x' and 'y' to have the same
uniques.
Ph.
On Wed, 2013-03-06 at 10:18 +0100, Philip K.F. Hölzenspies wrote:
Dear GHC-ers
Dear GHCers,
I have been experimenting some more with environments for lab work for
an FP intro course. One thing students tend to have difficulty with in
the initial labs are the error messages including type classes, or any
kind of more general type than they expected. I am trying to work
Dear GHCers,
On Wed, 2009-10-28 at 12:14 +, John Lato wrote:
This had me confused for a while, but I think I've worked out what's
happening. (+) is polymorphic, ...
Oh darn, it sounds like you're right. And polymorphism is so common. I
just came up with that example randomly as
Dear Luca,
The problem in your alternative code is that hGetContents lazily reads
the contents of the handle it is passed. You've run into a cognitive
bootstrap problem; the documentation for System.IO [1] does explain it,
but I can see that you need to understand it to be able to read it ;)
Dear GHCers,
Maybe this question is more for Haskell-cafe, but since it involves
language extensions as provided by GHC, it seems reasonable to post it
here.
The GHC user guide lists under 7.4 [1] the extensions to data types and
type synonyms. My question involves 7.4.5 (although the overlap
Dear Simon, et al.
I've looked around trying to pick up information on tiny installations
of Linux. It seems most modern distributions think 200MB is a pretty
barebone installation. There's a claim by someone that (s)he got a Tiny
Gentoo installation into 5MB. I'll be looking into that this
Dear GHCers,
I am trying to write a wrapper library for lab work to give to students.
My problem is, that the libraries I use require initialization that I
really want to hide from our students. The wrapper I'm writing is
compiled to a static library and installed with cabal, so students can
just
On Fri, 2009-04-24 at 13:06 +0200, Krzysztof Skrzętnicki wrote:
Why not just tell them to import your library and do something like
main = withSomeInit labMain
where withSomeInit is the function you provide? This approach is
present in some other libs that require initialization.
Dear
Dear all,
It seems that the front page of the developer wiki is rather
out-of-date. Considering that 6.10.2 is now at rc1-stage, I was rather
hoping to find some updated notes on release plans for 6.10.2 and what
will be in 6.12, but those notices are still at 6.8.3 and 6.10, resp.
On another
I've got the following code:
import Control.Exception
import System.Cmd
main = system sleep 1m `finally` putStrLn goodbye
When compiled with GHC 6.10.1.20090225, if I hit Ctrl-C during the
sleep, I get the goodbye printed twice. If I leave evaluation to
finish normally I get goodbye once.
On Friday 27 February 2009 09:39:14 Neil Mitchell wrote:
It looks like you are running in GHCi, which I think works. It's only
when the program is compiled and run from the command line (Cygwin or
DOS) that I get the above problem.
Dear Neil,
You were right. When I do compile it, though, I
Dear all,
My apologies for the lengthy mail. There is a question at the end about
whether all types in (of?) a kind closed under a type function can be
concluded to be a member of a type class (i.e. whether kind classes are
required for what I want to do).
I have been trying to reserect
On Thursday 04 December 2008 00:11:13 Ian Lynagh wrote:
If you have downloaded the source tarball then the preprocessed files
are included. Cabal may be getting confused by the .x files also being
present, so
rm src/Scan.x
should fix it. You may also need to
rm src/Parser.y
if you
On Thursday 04 December 2008 14:24:32 Philip K.F. Hölzenspies wrote:
[16 of 16] Compiling Main ( src/Main.hs,
dist/build/alex/alex-tmp/Main.o )
src/Main.hs:316:25:
Ambiguous type variable `e' in the constraint:
`GHC.Exception.Exception e'
arising from a use
Dear all,
Hopefully, you will excuse me for my lack of experience with Cabal. I have
seen quite a few e-mails on this list that seem related to this issue, but my
specific error, I did not find. Thus:
Since installing 6.10.1, I can't perform Setup.(l)hs functions. The error
message I get is:
On Friday 21 November 2008 10:49:47 Jules Bean wrote:
Philip Hölzenspies wrote:
Also, there are no de facto escape sequences, because special keys (like
function and arrow keys) have different sequences on different
terminals. A useful tip that may be useful to include in the wiki is an
Dear Ian, all,
After the announcement, I downloaded and installed the final release of
6.10.1. At some prior stage, I used the RC1 release, which had the same bug,
but I had generally assumed it to be an RC-phenomenon. Which bug? Well...
It seems editline has some incompatibility with my
L.S.,
First off, obviously, many thanks for all these usefull replies. A special
thanks to Chris. Your e-mail was very insightfull and instructive. I did, in
the end, decide to do my own queuing and scheduling using MVar () signaling,
guarding MVar a things. I want to avoid IORefs, because for
Dear GHCers,
I ran face first into an assumption I had made on MVar operations (in
Control.Concurrent); I had assumed there to be an atomic read (i.e.
non-destructive read, as opposed to destructive consume/take). The following
program illustrates what I had in mind.
testAtomic :: IO ()
On Wednesday 30 January 2008 10:13:01 Manuel M T Chakravarty wrote:
Upon inspection of the configure script, I found out that line 2651
uses the variable designating the ghc compiler.
This is due to a change of the configure stage that AFAIK was made to
easy building on windows. Instead,
Dear All,
I'm trying toupdate the Portfile so that ghc-6.8.2 can be built using MacPorts
(handy for installing other ghc-dependent material from MacPorts like
gtk2hs). The problem seems to be that the available bootstrap binary
On Tuesday 13 November 2007 12:27:02 Simon Marlow wrote:
maybe add a test right after the creation of DerivedConstants.h in
includes/Makefile:
DerivedConstants.h : mkDerivedConstantsHdr
./mkDerivedConstantsHdr $@
test -f $@ || exit 1
at least that will tell us whether it was
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