Error Loading Stdm.lhs in Haskell platform 2012
Dear Sir/Madam I Installed *Haskell Platform 2012.2.0.0 for Windowshttp://lambda.haskell.org/platform/download/2012.2.0.0/HaskellPlatform-2012.... *and try to load Stdm.lhs which is downloaded from http://www.dcs.gla.ac.uk/~jtod/discrete-mathematics/Stdm.lhs I have this error: stdm.lhs:1160:14: Parse error in pattern: n + 1 Failed, modules loaded: none. Is there anything I should do to make it right? Thank you. -- Iwan Awaludin
What version of ghc are you using?
In recent versions ghc doesn't support pattern matching of expressions
like (n+1).
You can rewrite that factorial function as
factorial n = n * factorial (n-1)
instead.
best,
Eugene
On 3 September 2012 22:08, Iwan Awaludin
Dear Sir/Madam I Installed Haskell Platform 2012.2.0.0 for Windows and try to load Stdm.lhs which is downloaded from http://www.dcs.gla.ac.uk/~jtod/discrete-mathematics/Stdm.lhs I have this error: stdm.lhs:1160:14: Parse error in pattern: n + 1 Failed, modules loaded: none.
Is there anything I should do to make it right? Thank you.
-- Iwan Awaludin
_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners
OK, I changed the line code as suggested. It is successfully compiled.
But it still has one warning:
stdm.lhs:38:10:
Warning: In the use of `catch'
(imported from Prelude, but defined in System.IO.Error):
Deprecated: "Please use the new exceptions variant,
Control.Exception.catch"
I don't know the effect but as long as I can use it for my course, I don't
mind. Thank you for your help.
On Tue, Sep 4, 2012 at 1:46 PM, Eugene Perederey wrote: What version of ghc are you using?
In recent versions ghc doesn't support pattern matching of expressions
like (n+1).
You can rewrite that factorial function as
factorial n = n * factorial (n-1)
instead. best,
Eugene On 3 September 2012 22:08, Iwan Awaludin Dear Sir/Madam
I Installed Haskell Platform 2012.2.0.0 for Windows and try to load
Stdm.lhs
which is downloaded from
http://www.dcs.gla.ac.uk/~jtod/discrete-mathematics/Stdm.lhs
I have this error:
stdm.lhs:1160:14: Parse error in pattern: n + 1
Failed, modules loaded: none. Is there anything I should do to make it right?
Thank you. --
Iwan Awaludin _______________________________________________
Beginners mailing list
Beginners@haskell.org
http://www.haskell.org/mailman/listinfo/beginners --
Iwan Awaludin
http://www.schoolofuniverse.com
The code for the book is written in Haskell '98, but recent versions of GHC default to Haskell2010. A salient difference between H98 and H2012 is the removed of n + k patterns which generates the error you are seeing. I can't find the exact command to use in the GHC docs to enable H98, but you could try the following old flag which disables GHCs extensions:
ghci -fno-glasgow-exts
I think the preferred command line invocation is:
ghci -XHaskell98
Strangely this seems to be missing in the GHC docs for Flags.
On 4 September 2012 17:40, Stephen Tetley
I can't find the exact command to use in the GHC docs to enable H98, but you could try the following old flag which disables GHCs extensions:
ghci -fno-glasgow-exts
participants (4)
-
Carlos J. G. Duarte -
Eugene Perederey -
Iwan Awaludin -
Stephen Tetley