在非成员函数中使用'this'无效

Question

我曾经在一个类上工作并开始在同一个.cpp文件中编写所有内容.但是,过了一段时间我可以看到这个类越来越大,所以我决定把它分成.h和.cpp文件.

gaussian.h文件:

class Gaussian{
    private:
        double mean;
        double standardDeviation;
        double variance;
        double precision;
        double precisionMean;
    public:
        Gaussian(double, double);
        ~Gaussian();
        double normalizationConstant(double);
        Gaussian fromPrecisionMean(double, double);
        Gaussian operator * (Gaussian);
        double absoluteDifference (Gaussian);
};

gaussian.cpp文件:

#include "gaussian.h"
#include <math.h>
#include "constants.h"
#include <stdlib.h>
#include <iostream>

Gaussian::Gaussian(double mean, double standardDeviation){
    this->mean = mean;
    this->standardDeviation = standardDeviation;
    this->variance = sqrt(standardDeviation);
    this->precision = 1.0/variance;
    this->precisionMean = precision*mean;
} 

//Code for the rest of the functions...

double absoluteDifference (Gaussian aux){
    double absolute = abs(this->precisionMean - aux.precisionMean);
    double square = abs(this->precision - aux.precision);
    if (absolute > square)
        return absolute;
    else
        return square;
}

但是,我无法编译.我尝试跑步:

g++ -I. -c -w gaussian.cpp

但我得到:

gaussian.cpp: In function ‘double absoluteDifference(Gaussian)’:
gaussian.cpp:37:27: error: invalid use of ‘this’ in non-member function
gaussian.h:7:16: error: ‘double Gaussian::precisionMean’ is private
gaussian.cpp:37:53: error: within this context
gaussian.cpp:38:25: error: invalid use of ‘this’ in non-member function
gaussian.h:6:16: error: ‘double Gaussian::precision’ is private
gaussian.cpp:38:47: error: within this context

为什么我不能用这个？我在fromPrecisionMean函数中使用它并编译.是因为该函数返回高斯函数吗？任何额外的解释都会非常感激,我尽可能多地学习!谢谢!

Answer 1

你忘了宣布absoluteDifference作为Gaussian班级的一部分.

更改:

double absoluteDifference (Gaussian aux){

对此:

double Gaussian::absoluteDifference (Gaussian aux){

附注:通过引用而不是值传递可能更好:

double Gaussian::absoluteDifference (const Gaussian &aux){