How does ruby do the + operator?

问题

Ruby does not support incrementing variables like variable++. I saw this behaviour that:

2 ++ 4

gives 6. In fact, any number of + signs between two variables are treated as one single +. How does ruby manage that? And since ruby does that, can it be taken as the reason for the unavailability of the ++ operator?

回答1:

This:

2 ++ 4

is parsed as:

2 + (+4)

so the second + is a unary plus. Adding more pluses just adds more unary + operators so:

2 ++++++ 4

is seen as:

2 + (+(+(+(+(+(+4))))))

If you provide your +@ method in Fixnum:

class Fixnum
  def +@
    puts 'unary +'
    self
  end
end

then you can even see it happen:

> 2 ++ 4
unary +
 => 6 

回答2:

Instead of ++ use += Example: a=2 a+=3 puts a

5

来源：https://stackoverflow.com/questions/24523329/how-does-ruby-do-the-operator