Detect unconnected nodes in input file and warn user
Nodes that aren't connected to anything can result in outputs that may confuse the user. The simulation currently runs anyway but gets a singular matrix with no results. For example, this circuit without a grounded negative input:
from circuit.liso import LisoInputParser
p = LisoInputParser()
p.parse("r r1 1k n1 ninp")
p.parse("op op1 op27 ninp ninm nout")
p.parse("r r2 100k nout ninp")
p.parse("uinput n1")
p.parse("uoutput nout")
p.parse("freq log 1 100k 1000")
p.show()
This prints...
usr/local/lib/python3.5/dist-packages/scipy/sparse/linalg/dsolve/linsolve.py:192: MatrixRankWarning: Matrix is exactly singular
warn("Matrix is exactly singular", MatrixRankWarning)
...but still attempts to plot the (empty) results.
The solver should check that the nodes are all connected to something.