[GAP Forum] Implementing automatic inheritance of features

[Thomas Breuer]

Dear Johannes,

GAP provides a standard mechanism for deriving information about
an object from known information about another object,
see Section ``Relations Between Domains'' of the GAP Reference Manual.

For example, if `g' is a group object and a subgroup is created via
`Subgroup( g, ... )' then certain properties and attributes which are
set (or not set) in `g' are used to derive certain properties and
attributes of the subgroup object
--think of `IsFinite' for `g' implying `IsFinite' for the subgroup.

This transfer of information happens only upon creation of the subgroup
(or one has to call the relevant function explicitly), that is,
the subgroup does not automatically benefit from information about `g'
that is obtained later in the GAP session.

If I understand your question right then you are asking for ``static''
information which is already known when the subgroups are created,
so perhaps this mechanism is of interest.

If also ``dynamic inheritance'' of information is needed then more
involved code is necessary.
Mohamed has implemented something like this in his GAP packages.

All the best,
Thomas


On Wed, Oct 09, 2013 at 05:20:28PM +0200, Johannes Hahn wrote:
> Hi everyone.
> 
> Is there a mechanism in GAP that allows one to declare that certain
> new features are inherited by associated objects in a certain way?
> As an example: Let's say I want to implement a category for ordered
> groups. Is there a way to tell GAP that subgroups of a ordered group
> are also ordered with the same ordering?
> 
> greetings
> Johannes Hahn.