Better error for missing ground

[endolith]

import ahkab

mycir = ahkab.Circuit('Simple Example Circuit')
mycir.add_isource('Isource', 'nA', 'nD', dc_value=1)
mycir.add_resistor('Rad', 'nA', 'nD', value=5)

opa = ahkab.new_op()
r = ahkab.run(mycir, opa)['op']

produces error:

  File "C:\Anaconda3\lib\site-packages\ahkab\dc_analysis.py", line 1007, in generate_mna_and_N
    N[elem.n2, 0] = N[elem.n2, 0] - elem.I()

IndexError: index 2 is out of bounds for axis 0 with size 2

Adding a ground makes it work:

import ahkab

mycir = ahkab.Circuit('Simple Example Circuit')
mycir.add_isource('Isource', 'nA', 'nD', dc_value=1)
mycir.add_resistor('Rad', 'nA', 'nD', value=5)
mycir.add_vsource('Vgnd', mycir.gnd, 'nC', dc_value=0)

opa = ahkab.new_op()
r = ahkab.run(mycir, opa)['op']

Is it possible to make this error more helpful?

[itdaniher]

Yes! This should totally be caught by a pre-check, well before generate_mna_and_N. I'm actually on vacation this week(!) but I'll be sure to fix this when I get a chance.

Thanks!

edit:markdown