Question

我用用户定义的函数编写了此代码，但似乎不起作用。我一直在努力找出错误的位置，持续几个小时。但是找不到任何东西。看起来问题出在传递参数。但是我不知道，我对此很陌生！

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

double solutionFun (double a, double b, double c) {

  double  delta, solution1, solution2;

  delta = b*b - 4*a*c;

  if (delta > 0 ){
    solution1 = (-b + sqrt(delta)) / (2*a);
    solution2 = (-b - sqrt(delta)) / (2*a);

    cout << "There are 2 solutions." << endl;
    cout << "The solutions are:";
    return solution1, solution2;
  }

  else if (delta == 0){
    solution1 = (-b) / (2*a);
    cout << "There is 1 solution." << endl;
    cout << "The solution is:";
    return solution1;
  }

  else {
    cout << "There is no solution.";
    return 0;
  }

}

int main(){

  double a ,b ,c;

  cout << "Please enter the values of a, b, and c respectively:";
  cin >> a ,b ,c;

  solutionFun(a ,b ,c);

  return 0;
}

Answer 1

此代码不是您获得多个输入的方式：

cin >> a ,b ,c;

您要：

cin >> a >> b >> c;

此代码不是您显示答案的方式：

cout << "The solutions are:";
return solution1, solution2;

您反而想要：

cout << "The solutions are:" << solution1 << " and also " << solution2;

Answer 2

有关代码有效性和所需行为的一些问题（不包括编码实践/设计）。首先，了解如何从solutionFun()返回多个值（当前定义为返回double) by using std :: vector -- even though you are not using anything returned in this piece of code. Second, you didn't print ( cout << {) the solution values themselves, and it seemed like you were going for it. Third, see how to use std :: cin`中的多个输入一行代码。固定版本是这样：

#include <iostream>
#include <cmath>
#include <vector>

using namespace std;

std::vector<double> solutionFun (double a, double b, double c) {

  double  delta, solution1, solution2;

  delta = b*b - 4*a*c;

  if (delta > 0 ){
    solution1 = (-b + sqrt(delta)) / (2*a);
    solution2 = (-b - sqrt(delta)) / (2*a);

    cout << "There are 2 solutions." << endl;
    cout << "The solutions are: " << solution1 << " and " << solution2;
    return {solution1, solution2};
  }

  else if (delta == 0){
    solution1 = (-b) / (2*a);
    cout << "There is 1 solution." << endl;
    cout << "The solution is: " << solution1;
    return {solution1};
  }

  else {
    cout << "There is no solution.";
    return {};
  }    
}

int main(){

  double a ,b ,c;

  cout << "Please enter the values of a, b, and c respectively:";
  cin >> a >> b >> c;

  auto result = solutionFun(a ,b ,c);

  for (auto scalar : result)
  {
    // Do something with a component, or don't return anything from the function : )
  }

  return 0;
}

Answer 3

另一种方法是在命令行中传递a='<?xml version="1.0" encoding="utf-8"?><!DOCTYPE note SYSTEM "Note.dtd"><book><name>ABC</name></book>' str1="" start=a.index('<!DOCTYPE') end=a.index('>',start) str1=a[:start] str1+='' str1+=a[end+1:] str1 #'<?xml version="1.0" encoding="utf-8"?><book><name>ABC</name></book>'变量：

solution

void solutionFun (double a, double b, double c, double& solution1, double& solution2, size_t& solution_count) { double delta; delta = b*b - 4*a*c; solution2 = 0.0; if (delta > 0 ){ solution1 = (-b + sqrt(delta)) / (2*a); solution2 = (-b - sqrt(delta)) / (2*a); solution_count = 2; cout << "There are 2 solutions." << endl; cout << "The solutions are: " << solution1 << " and " << solution2; return; } else if (delta == 0){ solution1 = (-b) / (2*a); solution_count = 1; cout << "There is 1 solution." << endl; cout << "The solution is: " << solution1; return; } else { cout << "There is no solution."; solution_count = 0; return; } }和solution1, solution2通过引用传递，这意味着该函数可以修改调用者的变量。

二次公式c ++-用户定义的函数

3 个答案: