Trouble using a Boolean function in a program

Question

I am having trouble using a boolean loop. I understand that they are true/false functions, however I when I run my program, it seems to always return the "true" value. Is main the one setting pass = true, or is it targetHR that set the value to true? I am stumped.

#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;
}

My goal is to have targetHR be the one that does the calculations, as well as tell the main function if true/false. I want main to only have a response that is dependent on targetHR.

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;
    }
}

I have tried solving the issue by changing true/false with 1/0, but that did not fix my problem, so I am assuming that is not the issue.

songyuanyao · Accepted Answer · 2015-11-11 01:50:46Z

2

it seems to always return the "true" value

Because you're not using Comparison operator, you're using Assignment operator, which will return the value assigned for check, so pass = true will always be true, and pass = false will always be false. You should change

if (pass = true)

to

if (pass == true)

or just

if (pass)

BTW: Some compilers (such as clang) will give warnings for it, don't ignore them.

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

edited Nov 11, 2015 at 1:50

answered Nov 11, 2015 at 1:30

songyuanyao

174k16 gold badges327 silver badges432 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Aaron T Maynard Over a year ago

Wow... I am actually rather dissapointed in myself... Thank you very much for spotting this. At least I know I was on the right track! :)

songyuanyao Over a year ago

@AaronTMaynard This is a common mistake, :) BTW, some compliers would give a warning for this, don't ignore it.

Tas Over a year ago

Visual Studio will also warn about it

Collectives™ on Stack Overflow

Trouble using a Boolean function in a program

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related