Basic iteration functionality for products of projective spaces

[sagetrac-gjorgenson]

Implement nth_iterate and orbit functions for morphisms/points of products of projective spaces. Also implement nth_iterate_map for morphisms.

CC: @bhutz

Component: algebraic geometry

Author: Grayson Jorgenson

Branch/Commit: fded196

Reviewer: Ben Hutz

Issue created by migration from https://trac.sagemath.org/ticket/19557

[sagetrac-gjorgenson]

Branch: u/gjorgenson/ticket/19557

[sagetrac-git]

Commit: 3831d5a

[sagetrac-git]

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

3831d5a

19557: implementation of the iteration functionality

[sagetrac-git]

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

920d997

19557: added example and fixed some spacing

[sagetrac-git]

Changed commit from 3831d5a to 920d997

[bhutz]

comment:5

Need to fix the merge issue.

From looking through the commits I see a couple things to fix:

in nth_iterate:
these checks are done in __call__ with better coercion, so not needed here.
if self.codomain()!=f.domain():
raise TypeError("Point is not defined over domain of function")

use .is_endomorphism() instead:
if f.domain() != f.codomain():
raise TypeError("Domain and Codomain of function not equal")

in nth_iterate_map
use is_endomorphism() check

[sagetrac-git]

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

1a13172	19557: Merged with new beta to fix merge conflict.
559811d	19557: changed checks

[sagetrac-git]

Changed commit from 920d997 to 559811d

[sagetrac-git]

Changed commit from 559811d to 37c4e69

[sagetrac-git]

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

f114f1b	19557: attempted conflict fix
37c4e69	19557: second merge attempt

[bhutz]

comment:9

That all checks out fine. Just one thing: I was wrong about __call__ doing the coercion checking. That is true for projective spaces, but not for products. I think you should put that check back in as some weird behavior can occur.

Go ahead and put that back in, then I'll mark this positive.

[sagetrac-git]

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

fded196

19557: added check back in

[sagetrac-git]

Changed commit from 37c4e69 to fded196

[sagetrac-gjorgenson]

comment:11

Alright, I added the check into orbit as well.

[vbraun]

comment:13

reviewer name

[bhutz]

Reviewer: Ben Hutz

[vbraun]

Changed branch from u/gjorgenson/ticket/19557 to fded196