f#功能耦合迭代:性能问题和首选函数样式。

I am getting through the excellent book "Real-World Functional Programming" by Tomas Petricek and Jon Skeet (two SO gurus, btw, thanks to both of them). The following function, at page 277, introduces a way of computing a three point average on an array taking into account side values as special ones:I am getting through the excellent book "Real-W