在程序中使用布尔函数时遇到问题

Question

我在使用布尔循环时遇到问题。我知道它们是 true/false 函数，但是当我运行我的程序时，它似乎总是 return "true" 值。是 main 设置 pass = true，还是 targetHR 将值设置为 true？我被难住了。

#include <iostream>
using namespace std;
bool targetHR(int, int);

int main()
{
    int age = NULL, heartbeat;
    while (age >= 0)
    {
        cout << "Enter your age: ";                    // Receives age from the user.
        cin >> age;
        if (age < 0)
        {
            break;
        }
        cout << "enter your heart beats per minute: "; // Receives heartbeat from user.
        cin >> heartbeat;
        bool pass = targetHR(age, heartbeat);
        if (pass = true)
        {
            cout << "You are in your target heart rate." << endl;
        }
        if (pass = false)
        {
            cout << "You are not in your target heart rate." << endl;
        }
        cout << endl;
    }

    return 0;
}

我的目标是让 targetHR 进行计算，并在 true/false 时告诉主函数。我希望 main 仅具有依赖于 targetHR.

的响应

bool targetHR(int age, int heartbeat)
{
    double maxHR, minTHR, maxTHR;
    maxHR = 220 - age;
    minTHR = maxHR * 0.60;
    maxTHR = maxHR * 0.70;
    // Debugging purposes.
    // cout << "Max heartrate: " << maxHR << endl << "Min Target HR: " << minTHR << endl << "Max Target HR: " << maxTHR << endl;

    if (heartbeat < minTHR || heartbeat > maxTHR)
    {
        return false;
    }
    else
    {
        return true;
    }
}

我尝试通过将 true/false 更改为 1/0 来解决问题，但这并没有解决我的问题，所以我假设这不是问题所在。

Answer 1

it seems to always return the "true" value

因为您没有使用 Comparison operator, you're using Assignment operator，这将 return 分配给检查的值，所以 pass = true 将始终是 true，而 pass = false 永远是 false。你应该改变

if (pass = true)

到

if (pass == true)

或者只是

if (pass)

顺便说一句：一些编译器（如clang）会给出警告，不要忽略它们。

warning: using the result of an assignment as a condition without parentheses
note: use '==' to turn this assignment into an equality comparison

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