Ralf Hemmecke wrote:
>
> On 05/26/2016 02:44 PM, Waldek Hebisch wrote:
> > oldk1331 wrote:
> >>
> >>> I'm not sure if this patch creates unnecessary parenthesis elsewhere.
> >>
> >> One change I noticed is "unparse(( t-1 )::INFORM)", it used to be
> >> "t+-1", after patch it's "t+(-1)", is it a bug that it doesn't return
> >> "t-1"?
> >
> > That is a tricky question. InputForm (and OutputForm) are supposed
> > to work for all domains. In abelian semigroup containing symbols
> > and integers 't + -1' makes sense, but 't-1' is undefined:
> > we can add integer '-1' to symbol 't', but there is no way to
> > subtract. In principle all nontrivial transformations should be
> > done in domains (where we have axioms like associativity, etc.).
>
> I still don't see why 't + -1' makes sense. I would always want this as
> "t+(-1)".
FriCAS parser parses 't + -1' the same as 't+(-1)', so both results
are equivalent from point of view of 'unparse'.
--
Waldek Hebisch
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