Rust NFA Regex Engine

A simple regex engine implemented in Rust using NFA (Non-deterministic Finite Automata) construction.

Features

• Parses a subset of regex patterns into an NFA.
• Supports:
  • Literal matching
  • Concatenation
  • Alternation (|)
  • Kleene star (*)
  • Plus repetition (+)
  • Optional (?) [if implemented in builder]
• Runs a basic match computation on input strings.

⚠ Note: Advanced regex features like lookarounds, character classes, and named captures are not yet implemented.

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Example Regex Patterns That Work

Here are some patterns you can test without hitting unimplemented features:

Pattern	Meaning
ab*c	'a' followed by zero or more 'b''s, then 'c'
`dog	cat`
a.*z	'a' followed by anything, ending with 'z'
xyz+	'x' 'y' and one or more 'z''s
`(a	b)c*`

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Running the Engine

1. Clone & Build

git clone https://github.com/yourusername/regex-nfa-engine.git
cd regex-nfa-engine
cargo build

Example Run

=== NFA Regex Engine ===
Choose an option:
0) Enter your own regex
1) ab*c    [an 'a' followed by zero or more 'b's, then 'c']
2) a*c|b+    [a's then c OR one or more b's]
3) hello|world    [matches 'hello' or 'world']
Enter choice: 1
Using regex: ab*c
Enter string to test (or 'quit' to exit): abc
For 'abc': true