Conditionals

## 4.1 Conditionals

Gnucap behavioral modeling conditionals are an extension of the ``AC'' and ``DC'' Spice source parameters.
The extensions ...

1. There are more choices, including an ``else''.
2. They apply to all elements (primitive components).
3. Each section can contain functions and options.

The following are available:

`AC`
  AC analysis only.
`DC`
  DC (steady state) value.
`OP`
  OP analysis.
`TRAN`
  Transient analysis.
`FOUR`
  Fourier analysis only.
`ELSE`
  Anything not listed.
`ALL`
  Anything not listed.

A value or function with no conditional keyword is equivalent to `ALL`. For SPICE compatibility, use only `DC`, `AC`, or nothing.
They are interpreted like a ``switch'' statement. In case of a conflict, the last one applies. A set of precedence rules applies when some keys are missing. It is SPICE compatible, to the extent the features overlap.

OP analysis
  OP, DC, ALL, TRAN, 0
DC analysis
  DC, ALL, OP, TRAN, 0
Transient analysis
  TRAN, ALL, DC, OP, 0
Fourier analysis
  FOUR, TRAN, ALL, DC, OP, 0
AC analysis, fixed sources
  AC, 0
AC analysis, other elements
  AC, ALL, 0

### 4.1.1 Examples

`V12 1 0 AC 1 DC 3`
  This voltage source has a value of 1 for AC analysis, 3 for DC. OP, Transient, and Fourier inherit the DC value.
`R44 2 3 OP 1 ELSE 1g`
  This resistor has a value of 1 ohm for the ``OP'' analysis, 1 gig-ohm for anything else. This might be useful as the feedback resistor on an op-amp. Set it to 1 ohm to set the operating point, then 1 gig to measure its open loop characteristics, hiding the fact that the op-amp would probably saturate if it was really left open loop.