随机数生成函数 [英] Random Number Gen as function

问题描述

该程序的目标是要有一个随机数生成器，我可以通过一个函数在主机上使用它.然后，来自随机数生成器的值将触发一个操作.它具有if语句，用于检查生成器中的值.我遇到的问题是两个字符串，都出现数字1-5"和数字6-10"，而不是if语句仅触发期望的内容，从而只会出现其中一个字符串.

The goal of this program is to have a random number generator that I can use in the main through a function. Then the values from the random number generator will trigger an action. This has if statements checking the values from the generator. The problem I am having is both strings, "Numbers 1 - 5" and "Numbers 6 - 10" appear instead of the if statements triggering only what is expected from them which would make only one of the strings appear.

#include <iostream>
#include <string>
#include <chrono>

void main()
{
    void RanNum1to10();
    int RanNum;
    int x;
    std::cin >> x;
    if (x == 2)
    {
        std::cout << "X = 2" << std::endl << std::endl;
        RanNum1to10();
        if (RanNum = 1||2||3||4||5)
        {
            std::cout << "Number 1 - 5" << std::endl;
        }
        if (RanNum = 6||7||8||9||10)
        {
            std::cout << "Number 6 - 10" << std::endl;
        }
    }
system("pause");
}

void RanNum1to10()
{
    (time(0));
    int RanNum;
    int x = 1+(rand() % 9 + 1);
    switch(x)
    {
        case 1:
            RanNum = 1;
        case 2:
            RanNum = 2;
        case 3:
            RanNum = 3;
        case 4:
            RanNum = 4;
        case 5:
            RanNum = 5;
        case 6:
            RanNum = 6;
        case 7:
            RanNum = 7;
        case 8:
            RanNum = 8;
        case 9:
            RanNum = 9;
        default:
            RanNum = 10;
    }
}

谢谢.

推荐答案

您需要使用

    if ( (RanNum == 1) ||
         (RanNum == 2) ||
         (RanNum == 3) ||
         (RanNum == 4) ||
         (RanNum == 5) )

代替

    if (RanNum = 1||2||3||4||5)

与其他 if 语句类似.

那是一个问题.

另一个问题是您所在的行:

The other problem is that you have the line:

int RanNum;

在 main 中，但是您尚未为其分配任何值.

in main but you have not assigned any value to it.

您已在 RanNum1to10 中为同名的局部变量分配了值，但不会更改 main 中的 RanNum 的值

You have assigned values to a local variable of the same name in RanNum1to10 but that won't change the value of RanNum in main.

您可以通过将 RanNum1to10 的返回值更改为 int 并从中返回随机数，并分配 RanNum1to10的返回值来解决该问题.到 RanNum .

You can address that problem by changing the return vaule of RanNum1to10 to int, and returning the random number from it, and assigning the return value of RanNum1to10 to RanNum.

更改行

void RanNum1to10();

到

int RanNum1to10();

更改行

    RanNum1to10();

到

    RanNum = RanNum1to10();

将 RanNum1to10 的实现更改为:

int RanNum1to10()
{
   return (rand() % 10 + 1);
}

更新，以回应OP的评论

由于运算符优先级，表达式 if(x = 2 || 3 || 4)等效于 if(x =(2 || 3 || 4))，等效于 x = 1;如果是(x).如您所见，这样的 if 语句的条件始终为true.

Due to operator precedence, the expression if (x = 2||3||4) is equivalent to if ( x = (2 || 3 || 4) ), which is equivalent to x = 1; if ( x ). As you can see, the conditional of such an if statement always evaluates to true.

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