Bool Datatype in C++

In this article, we’ll take a look at the Bool datatype in C++.

The bool data type is one that is there in C++ for quite sometime. This serves as a convenient and easy datatype for programmers to manage and write conditional statements using a boolean value, rather than an int.

However, remember that essentially, both bool and int are the same, with some small differences.

Let’s take a look at using this datatype, using a few examples!

The bool Datatype in C++

We can assign a variable of this datatype to only two values:

• true -> Equivalent to the integer value 1
• false -> Equivalent to the integer value 0

The following way shows how the variables are assigned.

bool var_1 = true; // Set var_1 to true
bool var_2 = false; // Set var_2 to false

Interestingly, if you try to print these variables using std::cout, you’ll only get their integer values.

#include <iostream>

int main() {
    bool var_1 = true;
    bool var_2 = false;
    
    std::cout << "var_1: " << var_1 << std::endl;
    std::cout << "var_2: " << var_2 << std::endl;

    return 0;
}

Output

var_1: 1
var_2: 0

Using bool data type in C++

The most common use of the bool datatype is for conditional statements. We can compare conditions with a boolean, and also return them.

The below snippet shows the comparison of a condition with a bool value.

#include <iostream>

int main() {
    int x = 10, y = 20;
    if ((x > y) == true)
        // The condition evaluates to true
        std::cout << "x > y\n";
    else
        // The condition evaluates to false
        std::cout << "x <= y\n";
    return 0;
}

Output

x <= y

We can also return conditional statements since they are also a bool. We can use this to directly return them in functions

For example, if you declare a boolean function to check if the first argument is greater than the second, you can directly return a conditional statement (x > y).

bool check_greater(int x, int y) {
    return (x > y);
}

This will return true if x > y, and false otherwise.

Conversion to int/float/double

Since the default value of true is 1 (or 1.00), we can also convert them into an int/ float/ double by type casting.

Sometimes, even the compiler implicitly converts a bool to an int/ float, and vice-versa. So this is very convenient now!

The below expression is valid in C++:

int x = 10;
float y = 2.5;
float z = x + y + true + false;

Here, since all the types can be converted to the left-hand side type float, z will be assigned a value of: 10 + 2.5 + 1 + 0 = 13.5

We can also do the reverse if the datatype of the LHS is bool.

int x = 10;
float y = 2.5;
bool z = x + y + true + false;

Here, z will be assigned true, since (bool)10 + (bool)2.5 + true + false = true + true + true + false = true!

Using bool as a template argument

Since bool is a valid data type, we can pass it as a template argument too.

For example, we can pass it as an argument to std::vector<T>, to construct a vector of bools!

#include <iostream>
#include <vector>

int main() {
    std::vector<bool> vec = {true, false, true, false};
    for (auto i: vec)
        std::cout << i << std::endl;
    return 0;
}

Output

1
0
1
0

Conclusion

In this article, we learned about the bool data type in C++, and how we can use it in different ways, to make our lives easier!

References

• cppreference.com section on Bool data type