Lexical Analysis - Introduction to Compiler Construction in a Java World - page 43

FIGURE 2.12 Repetition r.
5. If r is , then we just need an -move from the start state to the nal state.
FIGURE 2.13 -move.
6. If N r is our NFA recognizing the language described by r, then N r also recognizes the
language described by (r). Parentheses only group expressions.
Example. As an example, reconsider the regular expression (ajb)ab. We decompose this
regular expression, and display its syntactic structure in Figure 2.14.
FIGURE 2.14 The syntactic structure for (ajb)ab.
We can construct our NFA based on this structure, beginning with the simplest compo-
nents, and putting them together according to the six rules above.
We start with the first a and b; the automata recognizing these are easy enough to
construct using rule 1 above.