Feature #1468
Adjoin indets to a poly ring
Description
Make it easy to "adjoin" indets to a poly ring.
JAA thinks this means: given polyringQQ[x,y]
and new indets a,b
- create polyring
QQ[x,y,a,b]
- create embedding
QQ[x,y]
intoQQ[x,y,a,b]
-- just a PolyAlgHom - create "inverse" hom from
QQ[x,y,a,b]
intoQQ[x,y]
- put everything together into a convenient structure
- make it accessible from CoCoA-5
Requested by Julian Danner
Related issues
History
#1 Updated by John Abbott about 4 years ago
- what term ord on
QQ[x,y,a,b]
? For impl, it would be nice if the orderings were compatible (i.e. respected by the embedding) - can the new indets be indexed? e.g.
QQ[x,y,a[1..2]]
- what should the "inverse" hom do when applied to something outside the image of
QQ[x,y]
? - the convenient structure could be just a pair of RingHoms; or should the big ring be available as a field of the record?
KISS suggests making the "inverse" send all new indets to 0; it is then the caller's responsibility to ensure that it is applied only to values in the image (assume that this check is wanted).
SUGGESTION should the embedding be available to CanonicalHom
? That would be nice! How to achieve this? (probably a new issue)
#2 Updated by John Abbott about 4 years ago
- Related to Feature #992: Poly ring homomorphism to change ordering added
#3 Updated by John Abbott almost 4 years ago
- Status changed from New to In Progress
- % Done changed from 0 to 10
What should new indets be called? Should they be "new symbols"? Advantage is that there could be no problems with name clashes.
Where should the new indets appear relative to those already in the poly ring?
At least for a first impl, they could appear after the indets of the orig ring (at least by default).
The embedding hom is one which respects PPs (i.e. the image of a PP is a PP). The inverse almost respects PPs too (unless they map to 0); if the inverse hom maps the new indets to 1 then the inv hom does respect PPs (but is obviously not injective if applied to elems outside the image of the embedding).
REMINDER this does remind me that I was considering introducing certain types of subring (see #562) so that homs could be restricted to them. They could be useful in this context.
#4 Updated by John Abbott almost 4 years ago
- Related to Feature #562: Subrings added
#5 Updated by John Abbott 5 months ago
- Target version changed from CoCoALib-0.99850 to CoCoALib-0.99900