PK_ERROR_code_t    PK_CURVE_eval_with_tan_handed
(
--- received arguments ---
PK_CURVE_t         curve,           --- curve
double             t,               --- curve parameter
int                n_derivs,        --- number of derivatives
PK_HAND_t          hand_direction,  --- evaluation direction

--- returned arguments ---
PK_VECTOR_t        p[],             --- point and derivatives.
PK_VECTOR_t *const tangent          --- curve tangent
)


This function behaves like PK_CURVE_eval_with_tangent but takes an additional
direction argument.


Specific Errors:
    PK_ERROR_bad_parameter            cannot evaluate out of range
    PK_ERROR_at_singularity           failed to evaluate tangent at singularity
    PK_ERROR_too_many_derivatives     too many derivatives requested
    PK_ERROR_eval_failure             internal evaluator failure


Like PK_CURVE_eval_with_tangent this function evaluates a point, derivatives
and tangent at a given parameter on a curve segment determined by an
additional direction argument ( see the definition in PK_CURVE_eval_handed ).