subrings of the symbolic ring

[dkrenn]

We create subrings of the symbolic ring, which allow or reject a given set of variables.

CC: @behackl @cheuberg

Component: symbolics

Author: Daniel Krenn

Branch/Commit: d376b10

Reviewer: Benjamin Hackl

Issue created by migration from https://trac.sagemath.org/ticket/19259

[dkrenn]

Branch: u/dkrenn/symbolic-subring

[rwst]

comment:2

The (unregistered, yours?) patchbot seems to have problems, but probably not with this branch. I'm in favor of this enhancement as it allows some solutions to other tickets.

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Last 10 new commits:

4b8f9be	write workaround for #19231
8696a6e	extend `_coerce_map_from_` in rejecting-subring
30f7058	write doctests for coercions, common_parent, pushout
a54b4af	minor docstring rewriting of factory
fb2885c	subring in index.rst
eab9513	simplify a doctest
23352b2	change ValueError to TypeError to make everything work with SR as it should
2d8b7c4	typo in docstring
15ec40e	docstring of SR.subring
7938d95	module description of subring

[rwst]

Commit: 7938d95

[dkrenn]

comment:3

Replying to @rwst:

The (unregistered, yours?) patchbot seems to have problems, but probably not with this branch.

Yes, it is my patchbot. I think something related to the upgrade to beta7 ...

I'm in favor of this enhancement as it allows some solutions to other tickets.

Good :)

(Which tickets are these?)

[rwst]

comment:4

Replying to @dkrenn:

Replying to @rwst:

I'm in favor of this enhancement as it allows some solutions to other tickets.

Good :)

(Which tickets are these?)

See comment 57 of #12967 by vbraun: "The symbolic constants, like pi.pyobject(), should be elements in some parent set. The symbolic constants can then coerce into the infinity ring, solving the pi.pyobject() < oo == False issue."

Consequently this would be good for #19040.

[novoselt]

comment:6

This is fantastic! Don't plan to review it as I am not an expert on coersion stuff, but looks very good. I am only not quite sure that only_constants deserves to be a parameter: it can be implemented by accepting no variables and if SR.subring(accepting_variables=()) looks bad and non-obvious, than perhaps there should be a shortcut for it SR.subring_of_constants()?

[dkrenn]

comment:7

Replying to @novoselt:

This is fantastic!

Good to hear :)

Don't plan to review it as I am not an expert on coersion stuff, but looks very good.

You could review the non-coercion part ;)

I am only not quite sure that only_constants deserves to be a parameter: it can be implemented by accepting no variables and if SR.subring(accepting_variables=()) looks bad and non-obvious, than perhaps there should be a shortcut for it SR.subring_of_constants()?

My feeling is that some kind of shortcut to this special ring is convenient to have (and it is also good to mention this subring explicitly somewhere). Thus, +1 that there is some kind of explicit way to create the subring of symbolic constants.
However, I am open on how this should be achieved. My indention was having one method subring which can create all kind of subrings (cf. Unix philosophy: Do One Thing and Do It Well).

[rwst]

comment:8

Ah, with constant you mean no symbols (maybe better clarify). Yeah I make that distinction in #19040 often enough so it seems very natural.

[dkrenn]

comment:9

Replying to @rwst:

Ah, with constant you mean no symbols (maybe better clarify). Yeah I make that distinction in #19040 often enough so it seems very natural.

Keyword only_constants --> no_symbols ? (And maybe all occurrences of variable --> symbol? What is the best terminology?)

[rwst]

comment:10

Replying to @dkrenn:

Replying to @rwst:

Ah, with constant you mean no symbols (maybe better clarify). Yeah I make that distinction in #19040 often enough so it seems very natural.

Keyword only_constants --> no_symbols ?

Or no_variables.

(And maybe all occurrences of variable --> symbol?

Not necessary IMO.