[m-rev.] for review: Fix digraph.tc and digraph.rtc.

[Peter Wang]

On Wed, 11 Jan 2023 00:11:30 +1100 Julien Fischer <jfischer at opturion.com> wrote:
> 
> On Tue, 10 Jan 2023, Peter Wang wrote:
> 
> > The implementation of digraph.rtc was incorrect (as demonstrated in the
> > new test case), which meant that digraph.tc was also incorrect.
> 
> Ouch!
> 

> > @@ -1048,14 +1069,24 @@ tc(G, Tc) :-
> >     % digraph.tc returns the transitive closure of a digraph.
> >     % We use this procedure:
> >     %
> > -    % - Compute the reflexive transitive closure.
> > +    % - Compute the reflexive transitive closure, which is
> > +    %   the reflexive closure of the transitive closure of G:
> > +    %       G* = (G+)=
> 
> What's that supposed to mean?
> 

Some notation I saw here
https://proofwiki.org/wiki/Category:Reflexive_Transitive_Closures

I've changed it to read

    % - Compute the reflexive transitive closure (denoted G*), which is
    %   the reflexive closure of the transitive closure of G (denoted G+).

to make the following text understandable.

Peter