For linear systems, see :meth:`Matrix.solv`.
.. function:: prmat
Prints the form of the matrix defined by :ref:`eqn <keyword_eqn>` statements. Each nonzero
element is printed as an "*".
.. function:: solve
Does one iteration of the non-linear system defined by :ref:`eqn <keyword_eqn>` statements.
Returns the linear norm of the difference between left and right hand sides
plus the change in the dependent variables.
.. function:: eqinit
Throws away previous dependent variable and equation specifications
from :ref:`eqn <keyword_eqn>` statements.