Philippe Faes wrote:
Hugs (version februari 2000) keeps reporting unexpected ';' or unexpected '}' in files that don't even contain those characters. I know very little about Haskell (I just started to try and study the language) so my haskell files will probably not be correct. Still with this kind of messages I have no clue of what to change in my programs. I don't know if this is a bug, or something I'm doing wrong. I'm using a Linux2.2 operating system on an i386 processor.
I attached a haskell source file (which is probably not even good haskell syntax), and the unexpected error message reported by hugs. The latter file was created typing: hugs tree.hs > hugserror.txt
Thank you,
Philippe Faes
mailto:Philippe.Faes@rug.ac.be
Hi Philippe, The ';' Hugs complains about is inserted automatically during lexical analysis, as part of the layout handling process. It marks the end of one definition, and the beginning of another. Often errors involving these ghost ';'s indicate that the layout is wrong. In your case, however, the source of the error is that you're using a data declaration for defining a type synonym on line 16. Since [Lijstelem] is not a correct right-hand side for a data declaration, the lexer assumes that the declaration of Lijst has ended and inserts a ';'. But since [Lijstelem] isn't a new declaration either, you get the error you mentioned. Write type Lijst = [Lijstelem] instead, and you'll be fine. All the best, Johan
------------------------------------------------------------------------ __ __ __ __ ____ ___ _________________________________________ || || || || || || ||__ Hugs 98: Based on the Haskell 98 standard ||___|| ||__|| ||__|| __|| Copyright (c) 1994-1999 ||---|| ___|| World Wide Web: http://haskell.org/hugs || || Report bugs to: hugs-bugs@haskell.org || || Version: February 2000 _________________________________________
Haskell 98 mode: Restart with command line option -98 to enable extensions
Reading file "/usr/local/share/hugs/lib/Prelude.hs": Parsing Dependency analysis Type checking Compiling Reading file "tree.hs": Parsing ERROR "tree.hs" (line 16): Syntax error in data type definition (unexpected `;', possibly due to bad layout) Prelude> [Leaving Hugs]
------------------------------------------------------------------------ -- haskell -- poging tot implementeren van trees en optimal search tree -- *** tree.hs *** -- cf cursus G&S p430
-- nieuwe types type Weight = Float type Cost = Float type Failweight = Weight type Token = Char
-- datastucturen data Tree = Failnode Weight | Branch Token Tree Tree
data Lijst = [Lijstelem] data Lijstelem = Le Weight Failweight
-- functies q :: Int -> Lijst -> Weight q 0 (Lelm _ fw):ls = fw q i l:ls | i>0 = q i-1 ls | i<0 = error "fout in q"
p :: Int -> Lijst -> Weight
c :: Int -> Int -> Lijst -> Weight c i i _ = 0 c i j l = (w i j l) + zoekmin
w :: Int -> Int -> Lijst -> Weight w 0 0 [] = error "fout in lijstbewerking in tree.hs" w i i l = q i w i j l = (w i j-1 l) + (q j) +(p j) -- er wordt niet gecontroleerd of i>j; dat zou een fout moeten opleveren
zoekmin :: Int -> Int -> Lijst -> Weight zoekmin i j l = (c i (zoekroot-1 l) l) + (c (zoekroot l) j l)
zookroot :: Int -> Int -> Lijst -> Int --moet nog geimplementeerd worden
optboom :: Int -> Int -> Lijst -> Tree optboom i i l = Failnode (q i) optboom i j l = Branch (optboom i zoekroot) (zoekroot) (optboom (zoekroot+1) j) -- deze syntax klopt niet