问题描述
任何人都知道这个许可证与非免费iPhone应用程序兼容的良好实现吗？
Anyone know of a good implementation of this whose license is compatible with non-free iPhone apps?
正如这个问题所示，Boost看起来非常精彩。但是，我可以说，它只能在C ++中使用。
As suggested in this question, Boost looks absolutely wonderful. But as best I can tell, it is only available in C++.
推荐答案
无需任何东西花哨。任何具有良好C99数学库（如iphone）的平台已经拥有您需要的一切 - 特别是 erfc 功能，这是一个轻微的变体：
No need for anything fancy. Any platform with a good C99 math library (like the iphone) already has everything you need -- specifically the erfc function, which is a slight variant:
#import <math.h>
double cumulativeNormal(double x) {
return 0.5 * erfc(-x * M_SQRT1_2);
}
注意这是标准正态分布（即均值= 0，方差= 1），你需要使用适当的缩放 - 所以对于某些均值和方差，它将是：
Note this is for the standard normal distribution (i.e. mean = 0, variance = 1), you'll need to use the appropriate scaling -- so for some mean and variance, it will be:
return 0.5 * erfc(((mean - x)/sqrt(variance)) * M_SQRT1_2);
如果您不需要双精度，请将双精度更改为浮点数，使用 erfcf function，并将文字更改为单精度文字。
If you don't need double precision, change the doubles to floats, use the erfcf function, and change the literals to single-precision literals.
请记住，Objective-C是C的极轻型扩展。每个C函数都是Objective-C函数，不需要包装或其他恶作剧。
Remember, Objective-C is an extremely light extension to C. Every C function is an Objective-C function, with no wrapping or other shenanigans required.
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