效绵鼎 RE's:Definition Basis 1:If a is any symbol,then a is a RE,and L(a) ={a}. o Note:{a}is the language containing one string,and that string is of length 1. Basis 2:E is a RE,and L(E)=e. Basis3:☑is a RE,andL(☑)=☑. 66 RE’s: Definition ◼ Basis 1: If a is any symbol, then a is a RE, and L(a) = {a}.  Note: {a} is the language containing one string, and that string is of length 1. ◼ Basis 2: ε is a RE, and L(ε) = {ε}. ◼ Basis 3: ∅ is a RE, and L(∅) = ∅