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Feature #113

Introduce PartialHom

Added by John Abbott about 12 years ago. Updated almost 10 years ago.

Status:
In Progress
Priority:
Normal
Assignee:
John Abbott
Category:
New Function
Target version:
CoCoALib-1.0
Start date:
23 Mar 2012
Due date:
% Done:

10%

Estimated time:
15.00 h
Spent time:
10.25 h

Description

Currently CoCoALib does not distinguish between proper homs and partial homs.

Thus we can create a (partial) RingHom from QQ to ZZ which is valid only for integers in QQ. We can create a RingHom from ZZ to QQ -- a genuine RingHom.
Composing them produces the identity RingHom from QQ to QQ; but this does not have the same behaviour as applying first the partial hom and then the proper hom!

We should introduce separate types for full and partial homs. If this proves to be problematic, a lesser solution would be to add a mem fn saying whether it is full or partial.

Related issues

Related to CoCoALib - Feature #562: SubringsNew2014-05-20

Related to CoCoA-5 - Design #635: Automatic mapping of RingElem (in operation with a compound value)Closed2014-10-22

History

#1 Updated by John Abbott over 11 years ago

  • Status changed from New to In Progress
  • Assignee set to John Abbott

JAA has made a first (incomplete) implementation.

Currently the names chosen are RingHom and PartialRingHom. It seems sensible to retain the name RingHom for true homomorphisms. Other ideas for partial ring homs are SubringHom and RingMap. Any suggestions regarding naming are welcome.

The current design is as follows:
  • an abstract base class RingHomBase; all implementation classes (incl partial homs) are derived from this class
  • added a virtual member fn IamPartial to RingHomBase
  • PartialRingHom is a (smart) pointer to an instance of type RingHomBase
  • RingHom is derived from PartialRingHom [note that it satisfies the "is-a" relationship] so that the compiler can easily convert from RingHom to PartialRingHom; a RingHom guarantees that its impl gives false as the result a call to IamPartial
  • assignment to RingHom from PartialRingHom is allowed but checks at run-time that the impl gives false as the result of a call to IamPartial

This design was chosen because it was the first that came mind. JAA is not entirely happy because the distinction between RingHom and PartialRingHom does seem somewhat artificial.

#2 Updated by Anna Maria Bigatti about 11 years ago

  • Category set to New Function

#3 Updated by Anna Maria Bigatti about 10 years ago

  • Target version set to CoCoALib-0.99533 Easter14

#4 Updated by John Abbott about 10 years ago

  • Target version changed from CoCoALib-0.99533 Easter14 to CoCoALib-0.99534 Seoul14
  • % Done changed from 0 to 10

My impl attempt failed; static typing in C++ did not help.

Now considering defining notion of subring (certain limited families!)

#5 Updated by John Abbott almost 10 years ago

  • Target version changed from CoCoALib-0.99534 Seoul14 to CoCoALib-1.0

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