trivial __copy__ and __deepcopy__ methods for number field elements

[mkoeppe]

(split out from #13811, follow-up on #32454)

Most Sage objects are immutable. Nevertheless, copy and deepcopy make copies (through pickling/unpickling) for them because we have not provided the classes with __copy__ methods (which should just return the object) and __deepcopy__ methods (which in many cases should just return the object).

sage: a = 0
sage: copy(a) is a
False

In this ticket, we take care of number field elements.

CC: @tscrim @nbruin @kwankyu @videlec @mezzarobba

Component: number fields

Author: Matthias Koeppe

Branch/Commit: e971073

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/32478

[mkoeppe]

Branch: u/mkoeppe/trivial___copy___and___deepcopy___methods_for_number_field_elements

[mkoeppe]

comment:2

As mentioned in #13811 comment:37, the change for NumberFieldElement leads to doctest errors.

---

New commits:

3791864	NumberFieldElement_quadratic.__copy__, __deepcopy__: Immutable, so just return self
8a8cfdc	NumberFieldElement.__copy__, __deepcopy__: Immutable, so just return self

[mkoeppe]

Commit: 8a8cfdc

[sagetrac-git]

Changed commit from 8a8cfdc to 31c393e

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

31c393e

sage.rings.number_field.maps.NameChangeMap: Do not rely on `__copy__` making an actual copy of an immutable element

[mkoeppe]

comment:5

The failures came from the defective pattern discussed in #13811 comment:49, fixed now.

[mkoeppe]

Author: Matthias Koeppe

[sagetrac-git]

Changed commit from 31c393e to dd0644f

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

dd0644f

sage.rings.number_field.maps.NameChangeMap: Do not rely on `__copy__` making an actual copy of an immutable element

[tscrim]

comment:8

A while-we-are-at-it, we probably should optimize def _copy_for_parent(self, parent): as

cpdef _copy_for_parent(self, Parent parent):

Otherwise LGTM.

[sagetrac-git]

Changed commit from dd0644f to c8124a9

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

c8124a9

sage.rings.numberfield: Make _copy_for_parent methods cpdef

[tscrim]

comment:10

Thank you.

Sorry, there one other doc thing I just noticed. For NumberFieldElement_quadratic.__deepcopy__(), the documentation is wrong as it does not return a copy.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

e971073

NumberFieldElement_quadratic.__copy__, __deepcopy__: Remove misleading doc

[sagetrac-git]

Changed commit from c8124a9 to e971073

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:12

Thank you. LGTM.

[mkoeppe]

comment:13

Thanks!

[vbraun]

Changed branch from u/mkoeppe/trivial___copy___and___deepcopy___methods_for_number_field_elements to e971073