在C ++中有类似numpy.logspace的东西吗？ [英] Is there something like numpy.logspace in C++?

问题描述

正如标题所说，我寻找一些生成日志空间值的函数，就像numpy.logspace，但是对于python。和想法？

As the title says, im looking for some function that generates log-spaces values, just like numpy.logspace does, but for python. And ideas?

推荐答案

标准库中没有这样的函数，但是，你可以轻松地编写自己的。由于C ++和Python的不同性质，函数不会是相同的。我建议使用generator-style函数对象：

There is no such function in the standard library, however, you can easily write your own. Due to the different nature of C++ and Python, the function isn't going to be identical. I'd recommend using generator-style function object:

template<typename T>
class Logspace {
private:
    T curValue, base;

public:
    Logspace(T first, T base) : curValue(first), base(base) {}

    T operator()() {
        T retval = curValue;
        curValue *= base;
        return retval;
    }
};

使用示例（40个值，以2开始，以1开头）：

Example usage (40 values with base of 2 starting with 1):

std::vector<double> vals;
std::generate_n(std::back_inserter(vals), 40, Logspace<double>(1,2));

要注释的示例解决方案：

Example solution to comment:

std::vector<double> pyLogspace(double start, double stop, int num = 50, double base = 10) {
    double realStart = pow(base, start);
    double realBase = pow(base, (stop-start)/num);

    std::vector<double> retval;
    retval.reserve(num);
    std::generate_n(std::back_inserter(retval), num, Logspace<double>(realStart,realBase));
    return retval;
}

generate_while的示例实现

template<typename Value, typename OutputIt, typename Condition, typename Generator>
void generate_while(OutputIt output, Condition cond, Generator g) {
    Value val;
    while(cond(val = g())) {
        *output++ = val;
    }
}

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