What is the meaning of `!!empty?`?
51160
What does !! mean in ruby?
33007
What does \s! do?
121399
Changed behavior of string.Empty (or System.String::Empty) in .NET 4.5
130312
Why aren't hash values for "nothing" (empty) defined as all zeros?
114378
How to check if the string is empty?
116241
Why do we say "[expletive] ALL" for "nothing"?
125502
Empty set literal?
132398
What is null in Java?
26008
Why there is a unique empty set?
123498
Is "empty set" an element of a set?
150825
Is an empty set equal to another empty set?
27495
Why is True returned when checking if an empty string is in another?
110677
How is an empty set truly "empty"?
123316
What does  mean?
108516
"Not empty" set in one word?
143719
How does !! work in bash?
23756
Why does one often see "null != variable" instead of "variable != null" in C#?