Why does Ruby have TrueClass and FalseClass instead of a single Boolean class?

Question

I was working on serializing values when found out about this one. Ruby has a TrueClass class, and a FalseClass class, but it has no Boolean class. I\'d like to

Answer 1

true and false could be managed by a Boolean class that held multiple values, but then the class object would have to have internal values, and therefore have to be de-referenced with every use.

Instead, Ruby treats true and false as long values (0 and 1), each of which corresponds to a type of object class (FalseClass and TrueClass). By using two classes instead of a single Boolean class, each class does not require any values and therefore can be distinguished simply by its class identifier (0 or 1). I believe this translates to significant speed advantages internal to the Ruby engine, because internally Ruby can treat TrueClass and FalseClass as long values that require zero translation from their ID value, whereas a Boolean object would have to be de-referenced before it could be evaluated.

Answer 2

The main reason is simply the fact that this is far quicker and simpler to implement boolean expressions as it is currently than with a Boolean class which would imply a conversion.

As Mongus Pong told you, when you write "if ", you ask the interpretor to evaluate the thing and then branch. If you had Boolean class, you'd have to convert the evaluation of thing into a Boolean before branching (one more step).

Remember that such a ->Boolean conversion would be available as a Ruby method in the Boolean class. This method could then be changed dynamically as any other Ruby method, allowing developer to mess up things completely (which is not so serious indeed) but clearly, this wouldn't allow the interpretor to optimize tests as they should.

Do you realize that it would replace a few CPU instructions operation by a complete method call, which is costly in Ruby (remember the "send" method processing)...