我如何解决这个 cmath 编译器错误？

Question

我对编码相当陌生。 我正在做一个带有函数调用的项目，我的 POW() 和 SQRT() 函数说它们没有在这个范围内声明。 我不是特别确定如何解决这个编译器错误并感谢任何反馈

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cstdlib>
using namespace std;

double average(double a,double b, double c, double d);
void stdev(double a, double b, double c, double d);
int main(){
    double num1,num2,num3,num4;
    char repeat;
    do{
    cout << "Enter four decimal numbers: ";
    cin >> num1 >> num2 >> num3 >> num4;
    average(num1, num2, num3, num4);
    stdev(num1,num2,num3,num4);
    
    cout << "Please enter y to continue: ";
    cin >> repeat;
    cout << endl;
    }
    while (repeat == 'y');
    return 0;
}
double average(double a, double b, double c, double d){
    double ave;
    ave = (a+b+c+d)/4;
    return ave;
}
void stdev(double a, double b, double c, double d, double average){
    double std, ave;
    std = SQRT(POW(a-ave,2)+POW(b-ave,2)+POW(c-ave,2)+POW(d-ave,2));
    cout << "The average = "<< ave << endl;
    cout << "The standard deviation of these numbers = "<<std<<endl;
    return;
    }

Answer 1

sqrt 和 pow 必须是小写的，并且您还错过了 stdev 函数定义的平均值。 https://www.cplusplus.com/reference/cmath/

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cstdlib>
using namespace std;

double average(double a, double b, double c, double d);
void stdev(double a, double b, double c, double d, double average);

int main() {
    double num1, num2, num3, num4;
    char repeat;
    do {
        cout << "Enter four decimal numbers: ";
        cin >> num1 >> num2 >> num3 >> num4;
        double avg = average(num1, num2, num3, num4);
        stdev(num1, num2, num3, num4, avg);

        cout << "Please enter y to continue: ";
        cin >> repeat;
        cout << endl;
    } while (repeat == 'y');
    return 0;
}

double average(double a, double b, double c, double d) {
    double ave;
    ave = (a + b + c + d) / 4;
    return ave;
}
void stdev(double a, double b, double c, double d, double average) {
    double std = sqrt(pow(a - average, 2) + pow(b - average, 2) + pow(c - average, 2) + pow(d - average, 2));
    cout << "The average = " << average << endl;
    cout << "The standard deviation of these numbers = " << std << endl;
    return;
}