Set inclusion (in)

Description

The in operator takes two operands, the left operand is of ordinal type and the right operand is of set type. The result of the operation is of boolean type and is true if the left operand is a member of the right operand, and is false otherwise.

Example

   'a'    in  ['a', 'b', 'c']    returns true
   'b'    in  ['a', 'b', 'c']    returns true
   'c'    in  ['a', 'b', 'c']    returns true
   'd'    in  ['a', 'b', 'c']    returns false
   'e'    in  ['a', 'b', 'c']    returns false
   'a'    in  []                 returns false