added OneMatrix for matrix expressions with only ones

[Upabjojr]

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Release Notes

• matrices
  • Introduction of OneMatrix, a matrix symbol representing matrices of only 1 entries.

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• matrices
  • Introduction of OneMatrix, a matrix symbol representing matrices of only 1 entries. (#16676 by @Upabjojr)

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* matrices
  * Introduction of `OneMatrix`, a matrix symbol representing matrices of only 1 entries.
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Update

The release notes on the wiki have been updated.

[sylee957]

Looks good.
But I think you may need to add to __init__.py, so that it can be loaded under sympy main module.

[sylee957]

Would these commented-out tests be made more meaningful?

And I don't think that the matrix multiplication can be defined here, unless n is 1.

[Upabjojr]

These are wrong. I shall remove them.

[sylee957]

I am not sure that matrices with symbolic dimensions can have its elements defined in explicit coordinates

[Upabjojr]

ZeroMatrix behaves like this (always returns zero). There should be a bounds check, but I don't think this is important. If you access a matrix containing only one element, you're pretty sure you get that element.

[codecov]

Codecov Report

Merging #16676 into master will increase coverage by 0.015%.
The diff coverage is 100%.

@@              Coverage Diff              @@
##            master    #16676       +/-   ##
=============================================
+ Coverage   73.825%   73.841%   +0.015%     
=============================================
  Files          619       619               
  Lines       159286    159311       +25     
  Branches     37386     37388        +2     
=============================================
+ Hits        117594    117637       +43     
+ Misses       36260     36239       -21     
- Partials      5432      5435        +3