Bug #736
QuotientRing: is it correct to prohibit quotient by ideal(1)?
Description
The quotient ring R/I where I=ideal(1) gives the trivial ring.
Currently the quotienting operation gives a specific error because we do not want users trying to compute in the trivial ring. However this also blocks reasonable operations such as dim(R/I) and multiplicity(R/I).
Should we really forbid the creation of the trivial ring?
History
#1
Updated by John Abbott almost 9 years ago
Updated by The problem arose while doing some computations for Ulrich where it was known/expected that some ideals would be ideal(1).
Is there an easy way to test whether an ideal is ideal(1)? We have IsZero, but not IsOne.
#2
Updated by John Abbott almost 9 years ago
Robbiano confirms that it is best to avoid the null ring (which has surprising properties such as 1 = 0).
ideal(1). What do you think about the readability of the following:
if 1 isin I then ....if IsOne(I) then ....
Given that IsZero already exists, it seems coherent to offer IsOne too (for which types of arg?)
#3
Updated by Anna Maria Bigatti almost 9 years ago
Updated by - Status changed from New to In Progress
- Assignee set to Anna Maria Bigatti
- % Done changed from 0 to 10
John Abbott wrote:
if 1 isin I then ....if IsOne(I) then ....
the first already works. The second should be easy to add (I can do it).
#4
Updated by Anna Maria Bigatti almost 9 years ago
- Status changed from In Progress to Resolved
- % Done changed from 10 to 30
done: added IsOne(IDEAL)
#5
Updated by John Abbott about 4 years ago
- Status changed from Resolved to Closed
- Target version changed from CoCoALib-1.0 to CoCoALib-0.99700
- % Done changed from 30 to 100
- Estimated time set to 1.11 h
This was presumably done about 4 years ago, but we forgot to close the issue...
Closing now.