January 2002 - Hugs-Bugs

(no subject)
by ich bins! 21 Jan '02

21 Jan '02

after installing windows xp hugs hugs cannot be run anymore...it exits always with the error "Illegal character escape sequence "\W" " and a window pops up : FATAL ERROR: Unable to load prelude reinstalling did not help. thanx for answering:]tim

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install problem (with fix)
by Jay Glascoe 18 Jan '02

18 Jan '02

hello Hugs Bugs! I had one small problem installing and running the latest graphics library (graphics-2.0.4) on Linux. Long story short: conflicting library files due to previous hugs installations. Old "NumExts.hs" shadowing new "NumExts.lhs" file. Short story long ;-) : runhugs -Pgraphics-2.0.4/lib/x11: graphics-2.0.4/demos/HelloWorld.hs yields the error ERROR "graphics-2.0.4/lib/x11/GraphicsWindow.hs" - Unknown entity "showHex" imported from module "NumExts" The problem was that there was an old "NumExts" library hanging on in the lib/exts dir # ls -lArt /usr/local/share/hugs/lib/exts/ total 964 -rw-r--r-- 1 root root 146 Apr 11 2001 NumExts.hs -rw-r--r-- 1 root root 4479 Jan 18 14:14 IOExts.hs -rw-r--r-- 1 root root 4769 Jan 18 14:14 HtmlBlockTable.lhs [...] -rw-r--r-- 1 root root 2252 Jan 18 14:14 NumExts.lhs [...] problem resolved by simply removing the offending "NumExts.hs" -- Jay Glascoe | Software Developer | COBITE

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Overlapping instances
by Sean Seefried 16 Jan '02

16 Jan '02

Why is it that this source file -- begin code -- class Numeric a where describe :: a -> String instance Integral a => Numeric a where describe n = "Integral" instance Floating a => Numeric a where describe n = "Floating" -- end code -- produces the error message -- begin code -- *** This instance : Numeric a *** Overlaps with : Numeric a *** Common instance : Numeric a -- end code -- even though I have overlapping instances turned on. The "+o" option. ------------------------------------------------ Sean Seefried School of ITEE The University of Queensland Ph: 3365 8301 Mob: 0416 338 636

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Overlapping instances (addition to last message)
by Sean Seefried 15 Jan '02

15 Jan '02

I am using Hugs98, December 2001 edition. I am using the -98 and the +o command line options. ------------------------------------------------ Sean Seefried School of ITEE The University of Queensland Ph: 3365 8301 Mob: 0416 338 636

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expression where definition
by rdt＠cs.queensu.ca 14 Jan '02

14 Jan '02

Hi. The "Hugs for beginners" section of the manual has the example Prelude> take 10 fibs where fibs = ... and this indeed works. But I don't see this syntax in the grammar for Haskell; where clauses are appended to declarations, not to expressions. Is this a Hugs extension? Bob T.

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uparrow at hugs prompt
by rdt＠cs.queensu.ca 12 Jan '02

12 Jan '02

Hi. On Linux, an uparrow navigation character at the Hugs prompt gives me the preceding expression, much like a shell. On our Solaris boxes here, the uparrow gives me Prelude> ^[[A Should I expect the Linux behaviour on Solaris? If so, where would the problem be in the Solaris environment? Bob T.

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(no subject)
by joosten＠Anaxagoras.com 09 Jan '02

09 Jan '02

I have performed research with Hugs quite a lot, and this is the first time I have run into a real bug. I have isolated the bug into the following program, which brings the Hugs interpreter down. Since an interpreter should be something that never "crashes" (it should generate error messages instead), I conclude that this must be a bug. Here is the program > testCycles rs = (paths, map shrink cycles) > where > shrink cycles = dropWhile (/=last cycles) cycles > (paths, cycles) = f (rd[[a]| (a,b)<-rs, not (a `elem` map snd rs)], []) > f (paths,cs) > | null paths' = (paths,cs) > | otherwise = f (paths++paths',cs++paths'') > where > paths' = rd[pth++[b]|pth<-paths, (a,b)<-rs, last pth==a, not (b `elem` pth)] > paths'' = rd[pth++[b]|pth<-paths, (a,b)<-rs, last pth==a, b `elem` pth ] > rd [] = [] > rd (x:xs) = x: rd [e|e<-xs, e/=x] It crashes when executed. Try for example the expression: testCycles [(1,4),(4,5),(7,8),(3,2),(2,7)] Yours, Stef Joosten

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graphics library problem -- solved
by Bernhard Reus 09 Jan '02

09 Jan '02

Hi, the problem with the makefile are the wildcards. Substituting them by the actual file list does the job. That's what we did (diff style): < gc_sources = X.gc Xlib.gc Xlib_StdDIS.gc < c_sources = cbits/auxiliaries.c --- > gc_sources = $(wildcard *.gc) > c_sources = $(wildcard cbits/*.c) An easy thing you may say but confusing for non makefile-experts. I overlooked that. This afternoon a colleague of mine made the right guess. Maybe you should not refer to wildcards in the distribution. Best, Bernhard

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hugs98-Dec2001.tar.gz on FreeBSD-4.4
by Wilhelm B. Kloke 08 Jan '02

08 Jan '02

There is a small glitch in the configuration from source, and the binaries,too. When I tried to install graphics-2.0.4.src.tar.gz, I had to change LEADING_UNDERSCORE to undefined manually in config.h and recompile. Otherwise hugs failed to find _initModule. -- Dipl.-Math. Wilhelm Bernhard Kloke Institut fuer Arbeitsphysiologie an der Universitaet Dortmund Ardeystrasse 67, D-44139 Dortmund, Tel. 0231-1084-257

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strange behavior of ":i"
by Levent Erkok 07 Jan '02

07 Jan '02

Hugs version: Out of the CVS repository. Load this file: (the syntax error is intentional.) ---------------------------------------------------- import IO x= ---------------------------------------------------- After Hugs complains that there's an error (rightly so), type this: ---------------------------------------------------- IO> :i IORef ---------------------------------------------------- Hugs goes into an infinite loop. I've looked at the code a bit. It dies down in the call to findName, on line 1810 of hugs.c. This call never returns. Also, two if statements on lines 1797 and 1798 of hugs.c look suspicious: if (!mod) { free(mod); mod = NULL; } if (!nm) { free(nm); nm = NULL; } Looks like the tests are inverted. (The above bug is not caused by this, even when I remove the !'s, it still goes into an infinite loop.) I've tried compiling after setting WANT_FIXED_SIZE_TABLES to 1 in prelude.h, but still the same. What's strange is that I can't repeat the bug using any other import (i.e. anything other than IO), or without causing a syntax error in the file. Really weird. -Levent.

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