PK_ERROR_code_t      PK_CURVE_find_length
(
--- received arguments ---
PK_CURVE_t           curve,      --- curve to receive message
PK_INTERVAL_t        interval,   --- parametric interval of curve

--- returned arguments ---
double        *const length,     --- nominal arc length of curve
PK_INTERVAL_t *const range       --- range bounding actual arc length
)


This function evaluates the arc length of that part of the given curve
specified by the given parametric interval.


The information is returned in the form of a calculated arc length and an
interval containing lower and upper bounds on the true arc length.
For curves of class PK_CLASS_line or PK_CLASS_circle, the returned length
is exact.  For all other curves, the length is an approximation.