根据主页Screen的描述 “Screen is a full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells. Each virtual terminal provides the functions of the DEC VT100 terminal and, in addition, several control functions from the ANSI X3.64 (ISO 6429) and ISO 2022 standards (e.g., insert/delete line and support for multiple character sets). There is a scrollback history buffer for each virtual terminal and a copy-and-paste mechanism that allows the user to move text regions between windows.

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Newton-Raphson Method

曲线f(x)有根c,取曲线上一点$(x_1,f(x_1))$, 过此点的切线交x轴$x_2$,过曲线上$(x_2,f(x_2))$的切线交x轴$x_3$,如此反复得到一个序列 $x_1,x_2,\cdot \cdot \cdot,x_n$ 逼近c值.

过$(x_n,f(x_n))$的切线方程为 $y-f(x_n) = f'(x_n),(x-x_n)$,假设此方程与x轴的交点为$x_{n+1}$, 即有: $0 - f(x_n) = f'(x_n)(x_n+1 - x_n)$, 即$x_{n+1} = x_n - \frac{f(x_n)}{f'(x_n)}$ <Eq. 1>.

下面利用此法来求一个数的开方。 $f(x) = x^2 - a$ 有根$\sqrt{a}$, 由$f'(x_n) = 2x_n$, 代入式<Eq. 1>可得$x_{n+1} = (x_n + a/x_n)/2$; 当i -> INF 时, $x_i$ -> $\sqrt{a}$;

C implementation

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我制作的pkgsrc

xlyrics: unix下的歌词秀软件   

点此下载

EVA: KDE下的QQ客户端     

点此下载

#cd /usr/pkgsrc/wip-cn 
#tar xjvf eva.tar.bz2 
#cd eva 
#make install clean

就可以啦。在我的机子(NetBSD 3.0.1 macppc)上测试通过。。 更新到eva-20070327

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Author's picture

Guangchuang Yu

Bioinformatics Professor @ SMU

Bioinformatics Professor

Guangzhou