单位圆的内插实现，里面有4种内插算法：拉格朗日插值、牛顿插值、分段线性插值、分段样条插值、以及插值误差范数估计-Interpolation to achieve the unit circle, which has four kinds of interpolation algorithms: Lagrange interpolation, piecewise-linear interpolation, sub-spline interpolation, as well as Norm interpolation error estimates, etc.