The scenario
The identifier regex [a-zA-Z_][a-zA-Z0-9_]* is compiled into an ε-NFA using Thompson construction, demonstrating explicit ε transitions for concatenation and Kleene star.
What is in this drawing
Read the decisions behind it.
01
Model the initial character class as a single transition from start to first_char
02
Use a loop state with ε exits to accept and ε loop-back for the star
03
Keep the accept state final with no outgoing edges
When teaching or implementing Thompson's construction for regex-to-NFA conversion, especially for identifiers with a required first character and optional subsequent characters.
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