ruby - Why can't a variable name end with `?` while a method name can?

Question

A method name can end with a question mark ?

def has_completed?
  return count > 10
end

but a variable name cannot.

What is the reason for that? Isn't it convenient to have variable names ending the same way too? Given that we usually can't tell whether foobar is a method or a variable just by looking at the name foobar anyway, why the exception for the ? case?

And how should I work with this? Maybe always to use has or is in the code?

if process_has_completed
  ...
end

if user_is_using_console
  ...
end

Answer 1

You'd have to ask Matz to get an authoritative answer. However,

• Ruby is an untyped programming language and a variable like finished? would imply a specific type (boolean) which appears somewhat contradictory to me.
• A question somewhat requires a receiver (who can answer the question). A method must have a receiver (the object the method is called on), so a question mark makes sense. A variable on the other hand has no receiver, it's a mere container.