Franz Lehner wrote:
>
> On Thu, Mar 17, 2011 at 07:23:46PM -0400, Bill Page wrote:
> > Could you give an example of defining Expression over a domain where
> > "nothing interesting is known"? I tried several things but so far I
> > have been unable to produce an example of a value in such a domain.
> perhaps not related to this, but anyways:
> Is it possible to 'encapsulate' other domains in Expression Integer?
> I would like to have formal expressions foo(b,a,r)
> where foo is a formal operator and b,a,r are elements of some domain
> (in my case, a group or monoid). I would like to manipulate expressions
> involving these and at the end be able to extract the group elements.
> Currently I am converting to OutputForm -> String -> Symbol,
> but this way the type information is lost.
>
As Martin wrote use operators. Main difference between nullary
operator and symbol is that you can attach extra data to operators
but can not to symbols. ATM there is no way to attach extra
information directly to expressions. In principle we could
add a special kind of kernel for this purpose, but I am not
sure how much this is needed. Currently AFAIK Martin needs
extra data in RECOP and I needed parameter counts for
'meijerG' and 'hypergeometricF'. Martin uses data attached to
operators and ATM I restricted special functions to base
domains which contain integers, so I can store integers just
as subexpressions.
--
Waldek Hebisch
[email protected]
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