Question

所以我试着建立一个简单的计算器，但我一直得到同样的错误＆＃34;非法的其他没有匹配，如果＆＃34;在我把第二个其他的搜索后，我搜索了另一个答案，但似乎没有任何帮助，如果有人能给我任何解决方法，我将不胜感激

   #include "stdafx.h"
   #include <iostream>

   using namespace std;

   int main() {

    int number_1;

    cout << "" << endl;
    cin >> number_1;

    int number_2;

    cout << "" << endl;
    cin >> number_2;

   int number_3 = number_1 + number_2;

   int number_4 = number_1 - number_2;

   int number_5 = number_1 * number_2;

   int number_6 = number_1 / number_2;

   if (number_1 + number_2) {

    cout << "" << number_3 << endl;
   }

   else {

    if (number_1 - number_2) {

        cout << "" << number_4 << endl;
    }
   }

   else {

    if (number_1 * number_2){ 
        cout << "" << number_5 << endl; 4
    }
         }


  else {

    if (number_1 / number_2) {

        cout << "" << number_6 << endl;
    }

   }

   cout << "Press enter to continue" << endl;
   cin.ignore(10, '\n');
   cin.get();


   return 0;
}

Answer 1

那是因为每个else语句（不包括最后一个块）必须与if块相关联。如果您想继续迭代这些选项，就像您正在尝试一样，您需要将代码更改为：

#include "stdafx.h"
#include <iostream>
using namespace std;

int main() {

    int number_1;

    cout << "" << endl;
    cin >> number_1;

    int number_2;

    cout << "" << endl;
    cin >> number_2;

    int number_3 = number_1 + number_2;
    int number_4 = number_1 - number_2;
    int number_5 = number_1 * number_2;
    int number_6 = number_1 / number_2;

    if (number_1 + number_2) 
        cout << "" << number_3 << endl;
    else if (number_1 - number_2) 
        cout << "" << number_4 << endl;
    else if (number_1 * number_2) 
        cout << "" << number_5 << endl; 4
    else if (number_1 / number_2) 
        cout << "" << number_6 << endl;

    cout << "Press enter to continue" << endl;
    cin.ignore(10, '\n');
    cin.get();

    return 0;
}

在我所知道的每种语言中，如下所述的陈述都是非法的：

if (/*some condition*/)
    /*do some action*/
else
{
    if (/*some condition*/)
        /*do some action*/
    else
        /*do some action*/
}
/*You're fine until right here...  The else is ALWAYS your last statement*/
/*It essentially says: "If we didn't meet ANY of our conditions, do this...*/
//Once you try doing this:
else
{
    //try doing something
}
//YOU MESSED UP
//We've already passed all the parameters we were testing

请记住：if(/*some condition*/)后面跟着你需要的else if(/*some condition*/)个，以及结束你的else阻止。

ALSO

应该注意的是，您实际上并未测试if语句中的任何条件 - 您正在完成操作。您绝对必须检查某种值（布尔值，数字或其他...）例如：

if (number_1 + number_2 != 0) 
    cout << "" << number_3 << endl;
else if (number_1 - number_2 != 0) 
    cout << "" << number_4 << endl;
else if (number_1 * number_2 != 0) 
    cout << "" << number_5 << endl; 4
else if (number_1 / number_2 != 0) 
    cout << "" << number_6 << endl;
else cout << "Invalid number." << endl;

Answer 2

当我看到你的直接问题和你提供的代码时，我看到已经回答了你的问题的答案和评论，首先要记住的是一个简单的规则，也应用了这样做的风格

if ... else if else {}阻止陈述的规则。
- 第一个语句以if（条件||一组条件）开头，它们将通过条件布尔比较或逻辑数学评估比较评估为true或false
  - 的实施例
    
    布尔值：if ( something (x) is true or false )
    
    逻辑：If ( somevalue (x) is <, >, <=, >=, !=, == somevalue (y)or someFunction or operation done to either (x) or (y) or both )

<强>风格

打开和关闭括号的缩进和使用if else if else

间距

嵌套循环

{}

我更喜欢带有起始括号的紧凑版本，它为以下任何内容定义了一个新的作用域：命名空间，类声明，函数定义，枚举，switch语句及其case语句，if ... else if else语句，while和while循环，for循环，try和catch语句。我更喜欢默认选项卡或4个空格，用于所有嵌套代码块语句或新（嵌套范围）的缩进。我更喜欢保留我的其他if，而不是在初始if语句的右括号的同一行，以便我知道它属于该代码分支。实施例

<强> MyStyle.cpp

// Here are a couple of different styles // Tip about indentation - single tab normally 4-5 white spaces // with 4 being most common sometimes 3, but very rare: // I prefer 4. Which ever indent spacing you decide to choose // make sure all of your code follows that convention. // Style 1a: Single Execution with omitted braces if ( some condition ) // Braces {} omitted // single execution; // Single Execution without any following // else if...else blocks // Next statement of execution that doesn't belong to the above if; // Style 1b: Single Execution with braces if ( some condition ) { // Beginning Brace Started on separate line. // single execution; } // next statement not belonging to if statement; // Style 1c: Single Execution with braces if ( some condition ) { // Opening Brace on Same Line as if statement. // some execution; } // next statement not belonging to if statement; // Style 2: Concerning else, if else, and if else else when using braces and indentation // Style 2a: Opening and closing block statement as well as conditions on separate lines. if ( condition ) { // Statement or statements of execution; } else if ( some other condition ) { // Statement or statements of execution; } else { // Statement or statements of execution; } // Style 2b: More compact if ( condition ) { // Statement or statements of execution; } else if ( some other condition ) { // Statement or statements of execution; } else { // Statement or statements of execution; } // These can be applied to nested loops as well.

关于你选择的风格的一般想法应该是：选择适合你的东西，坚持使用那种风格，只要该风格保持可读性并保持简单，以便其他读者或用户轻松遵循代码块或遵循你的学校，工作或团队使用的风格。

关于你的代码与你的if语句的条件有关，请考虑这一点。

int main() { if ( condition || conditions ) { // Do Work; } else if ( some other condition || conditions ) { // Do This Instead; } else { // Otherwise; Finish with this; } // Nested If else if else if ( ... ) { if ( ... ) { // code; } else if ( ... ) { // code; if ( ... ) { // code; } else { // code; } // maybe more code; } else { // some other code; } } else if ( ... ) { if ( ... ) { // code; } if ( ... ) { // code; } if ( ... ) { // code; } else { // code; } } else { // code; } return 0; }

非法的其他没有匹配的if

2 个答案:

ALSO