Feature #801: Test whether a symbol is in a ring - CoCoALib - CoCoA Project

Feature #801

Test whether a symbol is in a ring

Added by John Abbott over 8 years ago. Updated about 2 months ago.

Status:

New

Priority:

Normal

Assignee:

Category:

New Function

Target version:

CoCoALib-0.99880

Start date:

09 Nov 2015

Due date:

% Done:

Estimated time:

Spent time:

0.20 h

Description

Should there be a function which tests whether a given symbol is in given ring?

I am thinking of "recursive" semantics: check whether the symbol is an indet, if not check whether it is in the coeff ring.

What should be the type of the result? Boolean?

Related issues

History

#1 Updated by John Abbott over 8 years ago

Currently this operation is implemented in a hidden way inside RingBase::myNew(symbol).

The implementation there needs to be improved (as it can be slow when the ring contains many symbols); it also creates a "wasteful" copy of the list of all symbols in the ring.

Current the pseudo-ctor for a RingElem from a symbol produces either a RingElem or throws an exception. Note that the RingElem produced could be zero (or almost any other value): consider the image of x in the quotient ring ZZ[x,y]/(x).
Should the new function return a boolean?