PK_ERROR_code_t    PK_CURVE_find_min_radius
(
--- received arguments ---
PK_CURVE_t         curve,       --- curve
PK_INTERVAL_t      t_int,       --- parameter interval

--- returned arguments ---
int         *const n_radii,     --- number of radii returned
double      *const radius,      --- min radius of curvature
PK_VECTOR_t *const position,    --- pvec where minimum occurs
double      *const param        --- parameter for curve
)


This function finds the minimum radius of curvature of the given curve, its
position and parameter. The user passes in the parameter interval required and
the search is confined to that part of the curve lying inside it. To find the
interval for the whole curve (if unknown) the function PK_CURVE_ask_interval
should be used.


The function returns a minimum of the radius of curvature, where one exists for
the curve. There will be no minimum radius curvature returned for a straight
line case. The function can return n_radii = 0 (for infinite radius of
curvature) , or n_radii = 1 minima.

The information provided on each minimum is:

 1: The magnitude of the minimum radius of curvature there. This is held in
    'radius'.

 2: A position vector indicating where on the curve the minimum of the radius
    of curvature is achieved. Held in 'position'.

 3: The curve parameter at the minimum position. Held in 'param'.