substring ( lower : Integer, upper : Integer ) : String

Returns a string containing all characters from self, starting from index *lower* up to index *upper* included. Both *lower* and *upper* parameters should be contained between *1* and *self.size()* included. *lower* cannot be greater than *upper*.

Expression	Result
'substring operation'.substring(11, 19)	'operation'
'substring operation'.substring(1, 1)	's'
'substring operation'.substring(0, 1)	invalid