On Fri, Mar 09, 2012 at 08:10:17PM +0100, Waldek Hebisch wrote:
> Serge D. Mechveliani wrote:
> > 
> > On Fri, Mar 09, 2012 at 10:31:23AM +0100, Ralf Hemmecke wrote:
> > >> 2. Change the line after `-- (I)'   to the next (commented) line - of
> > >>                                                             Product(...),
> > >>     Change the line after `-- (II)'  to the next (commented) line - of
> > >>                                                   eDom := construct(...).
> > >> Then, the comipler reports the error of somewhat
> > >>                                          "SetCategory is not a LIST".
> > >>
> > >> But may be, I guess now -- why!
> > >> Because the class  SetCategory  is not a member of  SetCategory,
> > >> and even not of a LIST
> > >> (while Record does not apply such a restriction).
> > >> If so, then there remains only the first question.
> > >
> > 
> > > [..]
> > > You try to construct
> > >
> > >   Product(DomainConstruction, SetCategory)
> > >
> > > However, the following shows you that this cannot work.
> > > [..]
> > > You give "SetCategory" as "B". But SetCategory is not of type  
> > > SetCategory. So this must fail. 
> > 
> > I see.
> > 
> > > I agree, however, that the error message, is quite confusing.
> > 
> > Why? Before checking SetCategory, it, probably checks the membership to
> > LIST. And reports that it is not of LIST (so Product is not applicable).
> > If so, then the report is precise.
> 
> No.  The message with "LIST" in it reports internal problem in
> typechecker.  

And my noise has occurred useful!
So, in this case the Spad compiler must report something like 
 "Apparent user error: 
  Line No 24:  
  ... Product(DomainConstruction, SetCategory) ...
  Product  requires  SetCategory  for each component ... 
 ".

> 'Error detected within library code:'
> is for errors which Spad code found. 

What might this mean?

Regards,

------
Sergei
[email protected]

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