Laurent,
Because the String class does not provide the `+@’ method?
That doesn't prevent someone else from doing it:
irb(main):001:0> + ‘a’
NoMethodError: undefined method `+@’ for “a”:String
from (irb):1
irb(main):002:0> class String; def +@() ‘+’ + self end end
=> nil
irb(main):003:0> + ‘a’
=> “+a”
- Warren Brown