Matrix-related fixes in differential geometry

[jdemeyer]

These are changes which are needed because of #24742.

1. src/sage/schemes/riemann_surfaces/riemann_surface.py: New MatrixArgs object to deal with constructing matrices #24742 will disallow passing strings to the matrix constructor. It's a rarely used feature and hard to get right properly. The fix is easy: pass actual elements of the ring instead of the generator names. This is clearly the right thing to do.

2. src/sage/tensor/modules/comp.py: I needed to change _get_list() but I have to say that I don't understand what the code is supposed to do. I wrote the code the way I did mainly to pass doctests. I also added some documentation to reflect better what the _get_list() method does. I also got rid of the evil try/except block trying to construct a matrix but happily returning a list if that failed.

3. src/sage/manifolds/differentiable/metric.py: this is a consequence of the change in 2. and it looks like a sensible change.

CC: @egourgoulhon @tscrim

Component: geometry

Author: Jeroen Demeyer, Eric Gourgoulhon

Branch/Commit: 6ae84f1

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/24884

[jdemeyer]

Branch: u/jdemeyer/matrix_related_fixes_in_differential_geometry

[jdemeyer]

New commits:

bd532ab

Matrix-related fixes in differential geometry

[jdemeyer]

Commit: bd532ab

[jdemeyer]

Description changed:

--- 
+++ 
@@ -1 +1,7 @@
 These are changes which are needed because of #24742.
+
+1. `src/sage/schemes/riemann_surfaces/riemann_surface.py` are needed because #24742 will disallow passing strings to the matrix constructor. It's a rarely used feature and hard to get right properly.
+
+2. `src/sage/tensor/modules/comp.py`: I needed to change `_get_list()` but I have to say that I don't understand what the code is supposed to do. I wrote the code the way I did mainly to pass doctests, not because it's the right thing to do. I also added some documentation to reflect better what the `_get_list()` method does.
+
+3. `src/sage/manifolds/differentiable/metric.py`: this is a consequence of the change in 2. and it looks like a sensible change.

[jdemeyer]

Description changed:

--- 
+++ 
@@ -1,7 +1,7 @@
 These are changes which are needed because of #24742.
 
-1. `src/sage/schemes/riemann_surfaces/riemann_surface.py` are needed because #24742 will disallow passing strings to the matrix constructor. It's a rarely used feature and hard to get right properly.
+1. `src/sage/schemes/riemann_surfaces/riemann_surface.py`: #24742 will disallow passing strings to the matrix constructor. It's a rarely used feature and hard to get right properly. The fix is easy: pass actual elements of the ring instead of the generator names. This is clearly the right thing to do.
 
-2. `src/sage/tensor/modules/comp.py`: I needed to change `_get_list()` but I have to say that I don't understand what the code is supposed to do. I wrote the code the way I did mainly to pass doctests, not because it's the right thing to do. I also added some documentation to reflect better what the `_get_list()` method does.
+2. `src/sage/tensor/modules/comp.py`: I needed to change `_get_list()` but I have to say that I don't understand what the code is supposed to do. I wrote the code the way I did mainly to pass doctests. I also added some documentation to reflect better what the `_get_list()` method does.
 
 3. `src/sage/manifolds/differentiable/metric.py`: this is a consequence of the change in 2. and it looks like a sensible change.

[jdemeyer]

Description changed:

--- 
+++ 
@@ -2,6 +2,6 @@
 
 1. `src/sage/schemes/riemann_surfaces/riemann_surface.py`: #24742 will disallow passing strings to the matrix constructor. It's a rarely used feature and hard to get right properly. The fix is easy: pass actual elements of the ring instead of the generator names. This is clearly the right thing to do.
 
-2. `src/sage/tensor/modules/comp.py`: I needed to change `_get_list()` but I have to say that I don't understand what the code is supposed to do. I wrote the code the way I did mainly to pass doctests. I also added some documentation to reflect better what the `_get_list()` method does.
+2. `src/sage/tensor/modules/comp.py`: I needed to change `_get_list()` but I have to say that I don't understand what the code is supposed to do. I wrote the code the way I did mainly to pass doctests. I also added some documentation to reflect better what the `_get_list()` method does. I also got rid of the evil `try`/`except` block trying to construct a matrix but happily returning a list if that failed.
 
 3. `src/sage/manifolds/differentiable/metric.py`: this is a consequence of the change in 2. and it looks like a sensible change.

[tscrim]

comment:5

Changes LGTM (Eric, if you see something you do not like, feel free to revert).

[tscrim]

Reviewer: Travis Scrimshaw