Error: "expression must have integral or unscoped enum type"

Question

伙计们，我是新手，我试着寻找一个解决方案，但是，我并没有真正理解它，我正在写 shorthand 来了解如何将它们替换为其他代码片段，所以我运行跨越我添加的模数但是它给出了 "expression must have integral or unscoped enum type".

我不知道枚举类型到底是什么，他们的代码不是运行?

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

int main() {

    double b, x, y, z, a, c;

    c, b, x, y, z, a, c = 100;
    x += 5;
    y -= 2;
    z *= 10;
    a /= b;
    c %= 3; // "c" seems to be giving out that error?


    cout << b << x << y << z << a << c;


    return 0;
}

这里的问题是 "c" 给出了 "expression must have integral or unscoped enum type" 错误。

我知道模数的作用，它给出了 2 个数字之间的除法余数，但是在这种情况下我很困惑，因为它应该给出余数吗？语法错误吗？

Answer 1

c 是双精度数，因此不能使用模运算符 %.

改用fmod()。

所以改变这个：

c %= 3

对此：

c = fmod(c, 3);

正如 Slava 提到的，您可以使用 int 代替，如下所示：

int c = 5; // for example
c %= 3

不需要使用 fmod()。重要的是要了解模运算符 % 与 ints.

一起使用

正如πìντα ρέι 提到的，还有这个：Can't use modulus on doubles?

顺便说一句，Victor，你有这么多变量，但其中大部分都未使用或未初始化。您是否在启用所有警告的情况下进行编译？这是我在编译您的原始代码时得到的结果（生成错误的行已被注释掉）：

C02QT2UBFVH6-lm:~ gsamaras$ g++ -Wall main.cpp 
main.cpp:9:5: warning: expression result unused [-Wunused-value]
    c, b, x, y, z, a, c = 100;
    ^
main.cpp:9:8: warning: expression result unused [-Wunused-value]
    c, b, x, y, z, a, c = 100;
       ^
main.cpp:9:11: warning: expression result unused [-Wunused-value]
    c, b, x, y, z, a, c = 100;
          ^
main.cpp:9:14: warning: expression result unused [-Wunused-value]
    c, b, x, y, z, a, c = 100;
             ^
main.cpp:9:17: warning: expression result unused [-Wunused-value]
    c, b, x, y, z, a, c = 100;
                ^
main.cpp:9:20: warning: expression result unused [-Wunused-value]
    c, b, x, y, z, a, c = 100;
                   ^
main.cpp:10:5: warning: variable 'x' is uninitialized when used here [-Wuninitialized]
    x += 5;
    ^
main.cpp:7:16: note: initialize the variable 'x' to silence this warning
    double b, x, y, z, a, c;
               ^
                = 0.0
main.cpp:11:5: warning: variable 'y' is uninitialized when used here [-Wuninitialized]
    y -= 2;
    ^
main.cpp:7:19: note: initialize the variable 'y' to silence this warning
    double b, x, y, z, a, c;
                  ^
                   = 0.0
main.cpp:12:5: warning: variable 'z' is uninitialized when used here [-Wuninitialized]
    z *= 10;
    ^
main.cpp:7:22: note: initialize the variable 'z' to silence this warning
    double b, x, y, z, a, c;
                     ^
                      = 0.0
main.cpp:13:5: warning: variable 'a' is uninitialized when used here [-Wuninitialized]
    a /= b;
    ^
main.cpp:7:25: note: initialize the variable 'a' to silence this warning
    double b, x, y, z, a, c;
                        ^
                         = 0.0
main.cpp:13:10: warning: variable 'b' is uninitialized when used here [-Wuninitialized]
    a /= b;
         ^
main.cpp:7:13: note: initialize the variable 'b' to silence this warning
    double b, x, y, z, a, c;
            ^
             = 0.0
11 warnings generated.

Error: "expression must have integral or unscoped enum type"

Error: "expression must have integral or unscoped enum type"

c++

math

enums

operators

modulus