Personal notes for CSE20 - Discrete Mathematics for Computer Science. Taken Fall 2020, with professor Shachar Lovett. See Course Homepage Sets Recursive definition of sets Basis step: Specify finitely many elements of \(S\) Recursive step: Give a rule for creating a new element of \(S\) from known values existing in \(S\), and potentially other values. String The set \(\Sigma^*\)of strings over the alphabet \(\Sigma\) is defined recursively by Basis step: \(\lambda \in \Sigma^*\) (where \(\lambda\) is the empty string containing no symbols)