matrix_equations() fails on network with dependent source

[timchinowsky]

This code for a passive network works:

from lcapy import Circuit
a = Circuit("""
V1 1 0 ac; down
R1 1 2 1; right
L1 2 3 1; right=1.5
R2 3 0_3 1; down=1.5
C1 3_a 0_4 1; down
W 0 0_3; right
W 3 3_a; right
W 0_3 0_4; right
""")
a.draw()
eq = a.ac().matrix_equations()
display(eq)

Here is the circuit:

But this code, which has a controlled source, does not:

from lcapy import Circuit
cct = Circuit(
"""
V1 1 0_6 ac; down
R1 1 2 10000; right=2
C1 3 0 1.1e-9; down=2.5
R2 2 3 10000; down
C2 2 4_5 2.2e-9; right=2
E1 4_8 0_3 opamp 3_1 4_6 100000;
RL 4 0_3 1e3; down

W 0_1 0; right
W 0 0_3; right
W 3 3_1; right=0.5
W 4_5 4; right
W 0_6 0_1; right
W 4_7 4_1 ; right
W 4_8 4_1; down
W 4_6 4_7; down
W 4_5 4_8; down
;label_style=stacked
""")
cct.draw()
display(cct.transfer(1,0,4,0))
cct.ac().matrix_equations()

It calculates the transfer function correctly, but errors out on the call to matrix_equations(). Here is the circuit:

[mph-]

I've pushed a fix for this. However, I haven't managed to track down why SymPy takes so long...

[timchinowsky]

Thanks! Seems to work, but yes, slow.