中文说明：
分段求值：求值x的分段函数用法：y=分段求值（x，断点，funs）参数（输入）x-向量或要求值的点数组，通过函数断点-n个断点的列表，-inf和+inf隐式
English Description：
Segmented evaluation: evaluate the segmented function of X usage: y= segmented evaluation (x, breakpoint, funs) parameters (input) x-vector or point group of the required value, through the function breakpoint -n breakpoint list, -inf and +inf implicit