c++ - 1.＃QNAN错误C++

我是编程新手，正在尝试编写新程序。通过我的程序检查时，它返回错误代码1.＃QNAN。我试图隔离变量并研究答案，但是找不到任何解决方案。

我的代码:

 // This is a program to decide what culvert should be properly used for a specific installation
// using given measurements and data
//
#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>

using namespace std;
// initializing functions
double slope_function();
double cbasin();
// initializing classes: Subdivisions specs

//intitializing global variables
double edge_road =0;
double up_stream  =0;
double down_stream =0;
double tbm =0.0;

//double culv_length =0;
double slope = 0.0 ;
char street_name[1001];
int min_culv = 15;
double up_strm_culv =0;
double dwn_strm_culv =0;


int main (int nNumberofArgs, char* pszArgs[])
{
    cout<< "This program will allow the surveyor to double check their calculations\n";
    cout << "in deciding what size, type, and requirements are allowed for the\n";
    cout << "installation of culverts in Terrebonne Parish.\n\n";



// begin input
   cout << "what is the name of the street\nwhere the culverts will be installed: ";
   cin.getline (street_name,1000);
   cout << endl;
   cout << "What is the Benchmark: ";
   cin >> tbm;
   cout << endl;
   cout << "What is the elevation of the edge of the road: ";
   cin >> edge_road;
   cout << endl;
   cout << "What is the up-stream culvert size: ";
   cin >> up_strm_culv;
   cout << endl;
   cout << "What is the culverts up-stream inverted elevation: ";
   cin >> up_stream;
   cout << endl;
   cout << "What is the down-stream culvert size: ";
   cin >> dwn_strm_culv;
   cout << endl;
   cout << "What is the culverts down-stream inverted elevation: ";
   cin >> down_stream;
   cout << endl;
   cout << "What is the length of culvert requested: ";
   cin >> culv_length;


   cout << "Your slope is : ";
   cout << slope_function();
   cout << endl;
   cout << street_name;
   cout << endl;
   cout << cbasin();


    cout << endl;
  // wait until user is ready before terminating program
  // to allow the user to see the program results
  system ("pause");
  return 0;
}

// slope function
double slope_function()
{
    double riseoverrun = 0.0;
    slope = (up_stream - down_stream)/ culv_length;
    return slope;
}


// Catch Basin function
double cbasin ( )
{
    double cb = 0;
    cb = culv_length / 60;
    cout << endl;
    cout << "You need ";
   cout << cb;
   cout << " catch basins for this job.";
   cout << endl;
}

最佳答案

1＃QNAN是“安静的NAN”的字符串表示形式。 “NAN”是“非数字”，仅适用于浮点数和 double 数。

NAN实际上对于表示“空”值非常有用(而不是选择一些真实的数字并希望获得最好的数字，因为它的自然含义不需要该数字)。

如果某些数学运算“无效”，则可以返回NAN(例如，取负数的对数)。

您可以使用以下方法从C++生成QNAN:

double d = std::numeric_limits<double>::quiet_NaN();

NAN上的任何比较运算(==，
(您代码中的实际错误似乎是一个返回 double 但没有return语句的函数)。

qNaN

c++ - 1.＃QNAN错误C++