Paul Koning

I can see the point. But it was a nasty surprise when I was building a non-linear device model (of a carbon microphone). Fitted a polynomial to it with gnuplot, and was trying to figure out why that same polynomial with the same coefficients didn't reproduce the correct waveform in ngSPICE. Once I puzzled out the undocumented weirdness I got it to work as expected.

Ouch. So we have the same function name with different semantics depending on where it appears. That's very nasty, and not at all clear from the manual. The impression I got from the manual talking about the three parsers is that they have subtle differences in how parentheses are written or whether they can handle spaces. There wasn't anything that suggested that the same expression might have utterly different -- and very surprising -- semantics.

The page you refer to talks about PSPICE compatibility mode. I'm not using that. In default mode, "pwrs" does not exist. Attached is a small test program. It shows that the star-star operator is the same as the "pow" function -- and that function always returns a positive result (it raises abs(x) to the power y). The test also shows that pwr(x,y) returns pow(x,y) times sign(x). So if I want the mathematically correct power operation, I have to use pow(x,y) for odd y, and pwr(x,y) for even y. Meanwhile,...

pwr() and pow() and ** issue