coercing expressions to booleans
In Ruby, you may need to coerce an expression to an explicit boolean value.
This:
b = defined?(foo) ? true : false
becomes:
b = !!defined?(foo)
That is a double not (!) operator.
irb(main):001:0> !!false
=> false
irb():002:0> !!nil
=> false
irb(main):003:0> !!true
=> true
irb(main):