This module takes a set of control points $(P_i)_i$, given as the curve
{\em cv\_control\_pts}, and
generates one B-spline \index{B-spline} curve $P$ ({\em kspline})
which is a smooth interpolation \index{interpolation!of a curve} of the 
input curve:
\[
P(t) \, = \, \sum_{i=1}^{M} P_i N_{i-1,j}(t)
\]
where $N_{i,j}$ is the B-spline of order $j$ on the interval $[x_i,x_{i+1}[$.
The order $j$ of the spline is given by the \verb+-j+ option and must satisfy
$2 \leq j \leq M$ where $M$ is the number of control points.
The higher the order $j$, the smoother is the interpolation curve, but the 
input curve is better approximated with lower order.
The \verb+-s+ option allows to change the step for the parameter $t$ to compute
the curve $P$.

