我正在用 C++ 制作一个简单的计算器。然而,该程序并没有完全按照应有的方式运行。运行时,trig if 语句执行良好,但是基本算术 else 语句不起作用。我确定代码没有执行 else 语句,并且想知道如何修复它。 else 语句中的代码工作正常,因为我已经注释掉了 if 语句。帮助?
这是我的代码:
#include "stdafx.h"
#include <iostream>
#include <string>
#include <cmath>
int main()
{
double input = 0;
double firstnumber = 0;
double secondnumber = 0;
std::string function;
std::string operation;
std::cout << "Enter your calculation: ";
std::cin >> function;
if(function == "sin" || "cos" || "tan")
{
if(function == "sin")
{
std::cin >> input;
std::cout << "The sine is " << sin(input) << std::endl;
system("PAUSE");
}
else if(function == "cos")
{
std::cin >> input;
std::cout << "The cosine is " << cos(input) << std::endl;
system("PAUSE");
}
else if(function == "tan")
{
std::cin >> input;
std::cout << "The tangent is " << tan(input) << std::endl;
system("PAUSE");
}
}
else
{
firstnumber = ::atof(function.c_str());
std::cin >> operation;
std::cin >> secondnumber;
double valueadd = firstnumber + secondnumber;
double valuesubtract = firstnumber - secondnumber;
double valuemultiply = firstnumber * secondnumber;
double valuedivide = firstnumber / secondnumber;
if(operation == "+")
{
std::cout << " = " << valueadd << std::endl;
system("PAUSE");
}
else if(operation == "-")
{
std::cout << " = " << valuesubtract << std::endl;
system("PAUSE");
}
else if(function == "*")
{
std::cout << " = " << valuemultiply << std::endl;
system("PAUSE");
}
else if(function == "/")
{
std::cout << " = " << valuedivide << std::endl;
system("PAUSE");
}
else
{
std::cout << "Error" << std::endl;
return 0;
}
}
return 0;
}
这条线是错误的。
if(function == "sin" || "cos" || "tan")
它应该是
if((function == "sin") || (function == "cos") || (function == "tan"))
请注意,该检查实际上是没有意义的,因为您已经分别检查了它们。你可以通过这样做来整理这个if
, else if
, else
chain.
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