Indexed SR variables

[mforets]

Provide a keyword argument to construct a tuple of symbolic variables:

sage: SR.var('x', 4)
(x0, x1, x2, x3)

CC: @nbruin @kcrisman @rwst

Component: symbolics

Keywords: symbolic ring

Author: Marcelo Forets

Branch/Commit: 29c9c2d

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/22909

[mforets]

Commit: 3093d25

[mforets]

comment:1

Related to: #22813, #22809, and #11576.

---

New commits:

7b8eb5f	add index keyword in SR.var
3093d25	add multiple indexing error

[mforets]

Author: Marcelo Forets

[mforets]

Branch: u/mforets/22909

[tscrim]

comment:2

This change is backwards incompatible with var('x','y'), where the second argument is treated as the latex name. We should also handle the latex name too.

The argument name of index is misleading. Perhaps n, index_set, indicies, or number?

Little thing, but the error messages should start with a lowercase letter (at least all new messages).

[mforets]

comment:3

Replying to @tscrim:

as usual, thanks for your prompt feedback!!

This change is backwards incompatible with var('x','y'), where the second argument is treated as the latex name. We should also handle the latex name too.

yes. with the current commit one has:

sage: SR.var('x', 'y')
...
AttributeError: 'str' object has no attribute 'is_integer'

instead of:

sage: SR.var('x', latex_name='y')
x
sage: latex(x)
{y}

should i do this with some type checking to handle (integer/string), or just ordering the arguments in a different way and expect user to always type index=...?

IMO, it is better if SR.var('x', 4) is understood by the program.

The argument name of index is misleading. Perhaps n, index_set, indicies, or number?

i used index because one speaks of "indexed variables". for those you suggest let me upvote (in order of preference): n and indices. in addition to those, let me add as options: len, length or size. what do others think?

Little thing, but the error messages should start with a lowercase letter (at least all new messages).

ok, and full stop yes or no?

the question is if an exception should be a complete sentence or not.

[tscrim]

comment:4

Replying to @mforets:

Replying to @tscrim:
This change is backwards incompatible with var('x','y'), where the second argument is treated as the latex name. We should also handle the latex name too.

yes. with the current commit one has:

sage: SR.var('x', 'y')
...
AttributeError: 'str' object has no attribute 'is_integer'

instead of:

sage: SR.var('x', latex_name='y')
x
sage: latex(x)
{y}

should i do this with some type checking to handle (integer/string), or just ordering the arguments in a different way and expect user to always type index=...?

As you surmised, you can do one of two things. The first is to put the n (index) as a later argument (I feel that domain is less used except as a keyword argument, so I'm more willing to let that be backwards incompatible). The second, and more preferable, is to check the input type and redirect as necessary. (This is one of the biggest shortcomings of weakly type languages.)

IMO, it is better if SR.var('x', 4) is understood by the program.

I agree. It just means some more complicated code to parse the inputs, but it has better useability.

The argument name of index is misleading. Perhaps n, index_set, indicies, or number?

i used index because one speaks of "indexed variables". for those you suggest let me upvote (in order of preference): n and indices. in addition to those, let me add as options: len, length or size. what do others think?

I think n is generic but clear enough for something like this. I don't have too much of a preference (but not index).

Little thing, but the error messages should start with a lowercase letter (at least all new messages).

ok, and full stop yes or no?

the question is if an exception should be a complete sentence or not.

They are generally not, at least by Python's standard. So no full stop nor uppercase letter.

[sagetrac-git]

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

8ad4a06	fix keyword name and exception formatting
751d7df	check input types and redirect as necessary

[sagetrac-git]

Changed commit from 3093d25 to 751d7df

[tscrim]

comment:6

I'm cc-ing Nils, Karl-Dieter, and Ralf to see if they have any comments before setting this to a positive review.