Re: WinHugs extremely basic newbie question

Hello Risto,

I don't have a Windows system myself, and therefore no winhugs, but your=20
problems seem unrelated to winhugs as such, so I will try to indicate how y=
ou=20
might proceed, using my Linux Hugs for illustration.

On Thursday 06 September 2007 14:13, Risto Rangel Kuoppa wrote:
> Hello everyone,
>=20
> I am having troubles to start using WinHugs.  I downloaded it, installed,
> and run it.  Yet I am unable to run something else than just evaluating
> expressions.  For example, I am trying to define my first data type with:
>=20
> Hugs> data Tipo =3D Cruz | Circulo deriving Eq

Quoting from the "The Hugs 98 User's Guide": "The Hugs prompt accepts=20
expressions, but not Haskell definitions." (See=20
http://cvs.haskell.org/Hugs/pages/users_guide/module-commands.html) So if y=
ou=20
wish to work with definitions, you have to put them in a file and either li=
st=20
the file on the hugs command line (this is not winhugs) or load the file fr=
om=20
the hugs promt. Here is what it would look like on a Linux system:

> tn@linux:~/tn/tmp/hugs> cat Risto1.hs
> data Tipo =3D Cruz | Circulo deriving Eq

("cat" is the Linux "type" command.)

> tn@linux:~/tn/tmp/hugs> hugs
> __   __ __  __  ____   ___      _________________________________________
> ||   || ||  || ||  || ||__      Hugs 98: Based on the Haskell 98 standard
> ||___|| ||__|| ||__||  __||     Copyright (c) 1994-2003
> ||---||         ___||           World Wide Web: http://haskell.org/hugs
> ||   ||                         Report bugs to: [email protected]
> ||   || Version: November 2003  _________________________________________
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> Haskell 98 mode: Restart with command line option -98 to enable extensions
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> Type :? for help
> Prelude> :load Risto1
> Main> Cruz
> ERROR - Cannot find "show" function for:
> *** Expression : Cruz
> *** Of type    : Tipo
>=20
> Main> :type Cruz
> Cruz :: Tipo
> Main>=20

=46rom this, you can see that hugs has indeed "got" the data definition. (T=
o=20
enable values of type Tipo to be printed, you should derive Show in additio=
n=20
to Eq.)

>=20
> But all I get is:
> ERROR - Syntax error in expression (unexpected keyword "data")
> Hugs>
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> I think that I must load some module or library but when I make:
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>=20
> Hugs> :load "C:\\Program
> Files\\WinHugs\\packages\\hugsbase\\Hugs\\Prelude.hs"
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> I get:
> ERROR file:.\Prelude.hs - Module "Hugs.Prelude" already loaded
> Hugs.Prelude>

Here, you are trying to load the standard prelude, but that is loaded alrea=
dy=20
by default, so the error message tells you exactly that. As indicated, you=
=20
should probably create your own file, containing your definitions, and then=
=20
load that.

>=20
> And I cannot find any Data.hs (Does it actually exist?) anywhere.

I am not sure what you are getting at here. Please give some additional=20
information.

I hope that you will be able to get past some of the initial hurdles. If no=
t,=20
or if you have additional questions, please feel free to ask again.

Best regards
Thorkil

> Could=20
> someone help me with this please? I have already spent several hours
> trying to figure it out.  All I want is to start testing the tutorials and
> learn Haskell but I am missing something to run them with WinHugs.
>=20
> Thanks in advance,
>=20
> Risto
>=20
>=20
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>=20