[Hugs-users] Hugs98-plus-Sept2006

[Mark Hills]

> Module names are built reflecting the directory structure, with separate
> starting directories for different products. If you start Hugs and type
> :set, you will see something like this for the search path:
> 
> Search path     :
> -P.:{Home}/lib/hugs/packages/*:/usr/local/lib/hugs/packages/*:{Hugs}/packages/*
> 
> So, each directory under lib/hugs/packages is added to the path,
> including (for instance) base and hugsbase. The hugsbase directory
> contains a Hugs directory, which contains a Prelude.hs file. Looking at
> the file, you will see that it says it defines module Hugs.Prelude,
> which makes sense since the file name is Hugs/Prelude.hs. Similarly with
> Data.Map, which is under the base directory in file Data/Map.hs.
> 
> I only have two files named Prelude.hs, the one under base and the one
> under hugsbase.

Same for me in /usr. I definitely got confused by the multiple instances
of Prelude.hs in /usr and in Hugs98 source. I'm recovering. Thanks for
the additional info (below).

Dave

>                 The one under base simply wraps the one under hugsbase
> (it imports it at the end), I'm assuming to allow the definitions to be
> Hugs-specific (since they use primitives) while still providing a
> standard location for the Prelude, in case you want to run your programs
> using a different Haskell system like GHC.
> 
> Mark
> 
> dfeustel at mindspring.com wrote:
> >> On Sat, Dec 09, 2006 at 09:38:37PM +0000, dfeustel at mindspring.com wrote:
> >>     
> >>> What I have discovered is that þugs, invoked with no arguments,
> >>> initializes itself differently depending upon the presence or absence
> >>> of Prelude.hs in the $HOME directory.  With Prelude.hs *not* present
> >>> in $HOME, I get the behavior described in the original post. When
> >>> Prelude.hs *is* present in $HOME, then an error re loading Prelude.hs
> >>> is reported, and primMinInt/primMaxInt/primMaxChar all work and the
> >>> prompt is 'Hugs.Prelude>'.
> >>>       
> >> You have a file called Prelude.hs containing a module Hugs.Prelude in
> >> your current directory.  When Hugs starts, it loads Hugs.Prelude, which
> >> it finds in the default path,
> >>     
> >
> > the 'find' command does not find a file by the name of Hugs.Prelude anywhere
> > in the Hugs98 tree or in /usr/local/lib/hugs, nor in the default path, as far
> > as I can tell. There are, þowever, 5 different instances of Prelude.hs in the
> > Hugs98 tree. Why is there more than 1 instance of Prelude.hs (with different
> > contents to boot) in Hugs98 source?
> >
> >   
> >>                               and then attempts to load Prelude from
> >> Prelude.hs (because . is at the front of the search path).  However this
> >> file contains a module Hugs.Prelude, not the Prelude it was expecting,
> >> and initialization fails.
> >>     
> >
> > Initialization does not fail. Hug terminates when initialization fails.
> > Initialization takes a different path when it encounters Prelude.hs in
> > either $HOME or . directories. The alternate initialization path makes hug
> > work as the Haskell book describes on page 13. Where is the module Hugs.Prelude
> > found during hugs initialization, if not in Prelude.hs?
> >  
> >   
> >> The error message when Hugs finds a file to contain the wrong module
> >> could be better, though.
> >>     
> >
> > I agree. Perhaps some standardization of terminology would help too.
> >
> > Dave
> > _______________________________________________
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> >