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c++ - 这个 BMI 计算器有什么问题？

问题描述

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

int main() {
  double lbs;
  double kg = lbs/2.205;
  double feet;
  double inches; 
  double height= ((feet * 12) + (inches))/39.37;
  double bmi=(kg)/(height * height);


  cout << "What is your weight (lbs)?" << endl;
  cin >> lbs;
  cout << "What is your height ? (feet only)" << endl;
  cin >> feet;
  cout << "What is your height ? (inches)" << endl;
  cin >> inches;
  cout << "Your BMI is : " << kg/(height*height);

}

最终输出为：inf。这意味着什么？

标签： c++

解决方案

考虑以下语句序列：

double lbs;
double kg = lbs/2.205;  // lbs is uninitialized here, oops
cout << "What is your weight (lbs)?" << endl;
cin >> lbs;

您lbs在从用户读取它之前使用它，事实上，在初始化它之前，它会调用未定义的行为。

您需要像这样重新排序语句：

double lbs;
cout << "What is your weight (lbs)?" << endl;
cin >> lbs;
double kg = lbs/2.205;  // compute kg after reading in lbs

你也需要对其他变量做类似的事情。

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