Contributed by StitchyPie

Bool

The primitive Bool scalar value used in Mojo.

init

var x = True
print(x)

var y: Bool = False
print(y)

True
False

fields

Bool stores it's data in the member variable value:

print(my_bool.value)

True

invert

Flips from True to False or vice-versa

print(True.__invert__())
print(~False)

False
True

equal

print(True.__eq__(True))
print(True == False)

True
False

not equal

print(True.__ne__(True))
print(True != False)

False
True

and

True if both values are True

print(True.__and__(True))
print(True & False)

True
False

or

True if any value is True

print(True.__or__(False))
print(False or False)

True
False

xor

Exclusive or, outputs true if exactly one of two inputs is true

print(True.__xor__(True))
print(True ^ False)
print(False ^ True)
print(False ^ False)

False
True
True
False

ror, rand and rxor

Think of the r as reversed, for example in a & b, if a doesn't implement __and__, then b.__rand__(a) will run instead.

For example create a struct MyNumber and implement __rand__ with a Bool:

struct MyNumber:
    var value: FloatLiteral
    fn __init__(inout self, num: FloatLiteral):
        self.value = num

    fn __rand__(self, other: Bool) -> Bool:
        print("Called MyNumber's __rand__ function")
        if self.value > 0.0 and other:
            return True
        return False

You normally can't compare a Bool with a FloatLiteral, but now we implemented __rand__ we can:

let my_number = MyNumber(1.0)
print(True & my_number)

Called MyNumber's __rand__ function
True

True.__and__(my_number) has no implementation, so it reverses it and runs my_number.__rand__(True) instead, with the special logic we implemented.