solve(x==x, x) returns [x == r1]

[pelegm]

Not sure if it's a bug or a problem with the documentation, but without any assumptions on x, solve(x==x, x) returns [x == r1]. The documentation does not state what r1 is, but gives the following example:

   If there is a parameter in the answer, that will show up as a new
   variable.  In the following example, "r1" is a real free variable
   (because of the "r"):

      sage: solve([x+y == 3, 2*x+2*y == 6],x,y)
      [[x == -r1 + 3, y == r1]]

However, without assumptions on x, there's no reason to believe that x is real.

This ticket also fixes a grammar issue introduced in #21554 (see comments).

Depends on #21554

Component: symbolics

Keywords: solve, days79

Author: Ashutosh Ahelleya

Branch/Commit: 224e064

Reviewer: Bryan Gin-ge Chen

Issue created by migration from https://trac.sagemath.org/ticket/21946

[sagetrac-aashu12]

Branch: u/aashu12/documentation

[sagetrac-aashu12]

Author: Ashutosh Ahelleya

[sagetrac-aashu12]

New commits:

c7acfd6	Fixes #21554
e8760d5	Fixed: #21946

[sagetrac-aashu12]

Commit: e8760d5

[dimpase]

Dependencies: #21554

[dimpase]

comment:6

what do you mean to say by

+    In case one of the solutions while solving an equation is a real number::

First of all, I would have written

+    In case one of the solutions of an equation is a real number::

Still, it's unclear what the following sequence of assumptions following this line has
to do with the one of solutions being real. Do you mean to say that in order to make sure that one (rather, every?) solution is real, you need to make the following assumptions? Something else?

[sagetrac-aashu12]

comment:7

Replying to @dimpase:

what do you mean to say by

+    In case one of the solutions while solving an equation is a real number::

First of all, I would have written

+    In case one of the solutions of an equation is a real number::

It was a part of ticket #21554 which has already been merged.

Still, it's unclear what the following sequence of assumptions following this line has
to do with the one of solutions being real. Do you mean to say that in order to make sure that one (rather, every?) solution is real, you need to make the following assumptions? Something else?

According to the documentation provided earlier, the solution of the equation described in the issue is r1, which is a real number (That is what the documentation says!). But the solution to this equation can be a complex number too! So, I just changed the documentation and redefined r1 to be any arbitrary constant. You can refer to this conversation: https://groups.google.com/forum/#!topic/sage-support/_XWjrYjk_3A

[dimpase]

comment:8

Replying to @sagetrac-aashu12:

Replying to @dimpase:

what do you mean to say by

+    In case one of the solutions while solving an equation is a real number::

First of all, I would have written

+    In case one of the solutions of an equation is a real number::

It was a part of ticket #21554 which has already been merged.

OK, I didn't notice this. But this makes no sense regardless, and you should fix it here.

Still, it's unclear what the following sequence of assumptions following this line has
to do with the one of solutions being real. Do you mean to say that in order to make sure that one (rather, every?) solution is real, you need to make the following assumptions? Something else?

According to the documentation provided earlier, the solution of the equation described in the issue is r1, which is a real number (That is what the documentation says!).
But the solution to this equation can be a complex number too! So, I just changed the documentation and redefined r1 to be any arbitrary constant. You can refer to this conversation: https://groups.google.com/forum/#!topic/sage-support/_XWjrYjk_3A

I understand this --- my question is wholly about the commit from #21554.
How does this docstring clarify anything about assuming non-integer? I don't get it.

[sagetrac-aashu12]

comment:9

Replying to @dimpase:

I understand this --- my question is wholly about the commit from #21554.
How does this docstring clarify anything about assuming non-integer? I don't get it.

No. The commits are different. I pushed them in different branches. But they showed up when I changed the author name.
That was what my doubt was about -> https://groups.google.com/forum/#!topic/sage-support/iqqEhA4K2Gg

[dimpase]

comment:10

Replying to @sagetrac-aashu12:

Replying to @dimpase:

I understand this --- my question is wholly about the commit from #21554.
How does this docstring clarify anything about assuming non-integer? I don't get it.

No. The commits are different. I pushed them in different branches. But they showed up when I changed the author name.
That was what my doubt was about -> https://groups.google.com/forum/#!topic/sage-support/iqqEhA4K2Gg

Differently named branches always have some common commits (and as I wrote on sage-support, it is the case that the commit c7acfd6 from #21554 is present in the branch here). Branch names are merely labels in the directed graph of commits in a repo.

Anyhow, c7acfd6 needs fixing, if only because it's broken English there...

[sagetrac-aashu12]

comment:11

Replying to @dimpase:

Differently named branches always have some common commits (and as I wrote on sage-support, it is the case that the commit c7acfd6 from #21554 is present in the branch here). Branch names are merely labels in the directed graph of commits in a repo.

Anyhow, c7acfd6 needs fixing, if only because it's broken English there...

Yea, I will fix it :)

[sagetrac-git]

Changed commit from e8760d5 to b881047

[sagetrac-git]

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

b881047

Fixed #21946

[sagetrac-git]

Changed commit from b881047 to ea063c3

[sagetrac-git]

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

ea063c3

Fixed #21946 and added example for #21554

[bryangingechen]

comment:14

This no longer merges.

[bryangingechen]

comment:15

I fixed the merge conflict. Unless there are other outstanding objections, I'm setting this to positive_review as this is certainly an improvement to the docs.

---

New commits:

e8760d5	Fixed: #21946
b881047	Fixed #21946
ea063c3	Fixed #21946 and added example for #21554
224e064	Merge branch 'u/aashu12/documentation' of git://trac.sagemath.org/sage into 21946_solve_returns_r1

[bryangingechen]

Changed branch from u/aashu12/documentation to public/21946_solve_returns_r1

[bryangingechen]

Changed commit from ea063c3 to 224e064

[bryangingechen]

Reviewer: Bryan Gin-ge Chen

[vbraun]

Changed branch from public/21946_solve_returns_r1 to 224e064