A node in the expression tree representing an independent variable.
Used for expressing functions depending on a spatial variable or time
name (str) – name of the node
domain (iterable of str) – list of domains that this variable is valid over
*Extends –
A node in the expression tree representing time.
Extends: Symbol
A node in the expression tree representing a spatial variable.
name (str) – name of the node (e.g. “x”, “y”, “z”, “r”, “x_n”, “x_s”, “x_p”, “r_n”, “r_p”)
domain (iterable of str) – list of domains that this variable is valid over (e.g. “cartesian”, “spherical polar”)
*Extends –