SymPy matrix expressions, block matrices, tensor expressions

[mkoeppe]

https://docs.sympy.org/latest/modules/matrices/expressions.html

https://docs.sympy.org/latest/modules/tensor/tensor.html

See also:

• 30307 - Refactor Components into parent & element

• 31942 - _sympy_ methods for matrices and vectors

• 31946 - _sympy_ methods for tensor component classes

CC: @mjungmath @egourgoulhon @tscrim

Component: symbolics

Issue created by migration from https://trac.sagemath.org/ticket/31945

[mkoeppe]

Description changed:

--- 
+++ 
@@ -3,3 +3,7 @@
 https://docs.sympy.org/latest/modules/tensor/tensor.html

+See also: 
+- #30307 - Refactor Components into parent & element
+- #31942 - `_sympy_` methods for matrices and vectors
+- #31946 - `_sympy_` methods for tensor component classes