Add developer manual section on integer return values

[kwankyu]

Return values of type int lack useful
integer methods such as factor().

We add a section to the developer manual
recommending to return integers as Integer.

CC: @slel

Component: documentation

Keywords: integer

Author: Kwankyu Lee, Samuel Lelièvre

Branch/Commit: 5d54501

Reviewer: Nils Bruin, Samuel Lelièvre, Kwankyu Lee

Issue created by migration from https://trac.sagemath.org/ticket/32200

[kwankyu]

Branch: public/32200

[sagetrac-git]

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

145d600

Add a section to developer manual

[sagetrac-git]

Commit: 145d600

[kwankyu]

Author: Kwankyu Lee

[tscrim]

comment:5

I think something should be explicitly mentioned about __hash__ being a definite exception.

More in the bikeshedding category: I think this would be better placed before the IMPORTING section as it is more minor than hashing and coercion.

[sagetrac-git]

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

e75e957

Mention `__hash__` as a definite exception

[sagetrac-git]

Changed commit from 145d600 to e75e957

[sagetrac-git]

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

fbff9af

Add a whiteline

[sagetrac-git]

Changed commit from e75e957 to fbff9af

[nbruin]

comment:8

Replying to @tscrim:

I think something should be explicitly mentioned about __hash__ being a definite exception.

More in the bikeshedding category: I think this would be better placed before the IMPORTING section as it is more minor than hashing and coercion.

__len__ and __int__ are other examples, I think. Should we try to be exhaustive here?

[sagetrac-git]

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

da07eab

Add more exceptions