借助光栅原理，让屏幕发出的光只能从正面特定角度范围内看到，从而实现「大角度防窥」的效果：
I’ve also seen a number of influential folks and organizations promote the use of PRF for encrypting data.
，这一点在heLLoword翻译官方下载中也有详细论述
Note however that depending on as well as the distribution of colours in the palette, there may not always be an exact solution for any given . Instead we’ll say that we want to minimise the absolute error between and some linear combination , or .
// 易错点4：栈空时返回1而非i+1 → 仅i=0时正确，i0时（如i=3）会返回1而非4