double arshup(double g, double p, int *ierr);
Compute pressure factor based upon pressure factor 
.
| Argument | Intent | Description |
| g | in | Specific heat constant |
| p | in | Pressure fraction |
| ierr | out | (optional) Return status code. |
Specific heat ratio 
.
Given 
out of range.
Return Value
Density fraction 
or NAN on error.
. 
.