PK_ERROR_code_t  PK_CURVE_find_vector_interval
(
--- received arguments ---
PK_CURVE_t           curve,     --- curve
PK_VECTOR_t          vector_1,  --- first position vector
PK_VECTOR_t          vector_2,  --- second position vector

--- returned arguments ---
PK_INTERVAL_t *const interval   --- parameter interval bounded by vectors.
)


This function returns the parameter interval of a curve bounded by two
position vectors lying on the curve.


Specific Errors:
    PK_ERROR_not_on_curve              both vectors do not lie on curve


The position vectors must lie on the curve within SESSION precision.
The position vectors are parameterised onto the curve yielding say t1 and t2.

For non-periodic curves, the returned interval is

    [ min(t1, t2)  max(t1,t2) ].

For periodic curves, the range of the curve bounded by the returned interval
is that starting from t1 and going in the direction of increasing parameter
until vector_2 is reached. If vector_1 and vector_2 are the same within
SESSION precision, the range is all of the curve and the returned interval is

    [t1 t1+period].