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Feature #1645

Implement monic0(f) for the case monic(0)?

Added by Anna Maria Bigatti over 2 years ago. Updated 2 months ago.

Status:
In Progress
Priority:
Normal
Assignee:
-
Category:
Improving
Target version:
CoCoALib-0.99900
Start date:
17 Jan 2022
Due date:
% Done:

10%

Estimated time:
Spent time:
0.80 h

Description

/**/ monic(RingElem(P,0));

throws the error "Non-zero RingElem required". That's OK.
But the manual for monic says "if "F" is zero, it returns just zero."

Should we implement monic0 as well (analogue of preimage0) returning 0 for convenience?
Think of the case ideal([ monic(f) | f in phi(L) ]): here 0 might occur without being a real problem.

Related issues

Related to CoCoALib - Design #1647: Suppress zero from ideal generators? Detect 1 and simplify generators?Closed2022-01-20

History

#1 Updated by John Abbott over 2 years ago

Right now I would be inclined to change the manual.
I am not yet convinced that monic0 is a good idea. Can you convince me?

#2 Updated by Anna Maria Bigatti over 2 years ago

John Abbott wrote:

Right now I would be inclined to change the manual.
I am not yet convinced that monic0 is a good idea. Can you convince me?

I would keep monic as is, changing the manual.

I would add the function monic0 for the case in the description:

[ monic(f) | f in phi(L) ]

Quite often monic is used just for beautifying the output, and not for the mathematical properties. In such cases it is a nuisance to uglify the code.

We have encountered similar dilemmas for other functions: the "0", could be a handy way of unifying the look and behaviour of these functions.

#3 Updated by John Abbott over 2 years ago

  • Status changed from New to In Progress
Let's try to make a list of possible "0" functions, and their expected behaviour if given 0 as argument.
  • monic0(f) would give f
  • deg0(f) would give 0 or -1?
  • LC0(f) would give 0 of coeffring?
  • LT0(f) would give 1 (PP) maybe ??
  • LF0(f) would give 0

I do still feel uneasy about this proposal: all of the above fns "feel unclean".

#4 Updated by John Abbott over 2 years ago

  • Related to Design #1647: Suppress zero from ideal generators? Detect 1 and simplify generators? added

#5 Updated by John Abbott over 2 years ago

Anna says it is OK to have these "dirty" functions because their names are strange.
She suggests that they each have separate manual pages (so as not to spoil the "pure" pages of the "good" functions).

#6 Updated by John Abbott about 2 years ago

Since I am hoping to make a release quite quickly, I prefer to postpone this issue to the next release (so we have time to discuss it a bit more).

#7 Updated by Anna Maria Bigatti about 2 years ago

  • Target version changed from CoCoALib-0.99800 to CoCoALib-0.99850

John Abbott wrote:

Since I am hoping to make a release quite quickly, I prefer to postpone this issue to the next release (so we have time to discuss it a bit more).

ok, postponed

#8 Updated by John Abbott almost 2 years ago

If the purpose is to beautify some polys then we could also consider prim (see issue #1580 and #1668).

#9 Updated by John Abbott 2 months ago

  • Target version changed from CoCoALib-0.99850 to CoCoALib-0.99900

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