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RegExp Theory

RegExp Theory. Finite State Machines. What is a FSM?. Used in CS theory classes Learned before more complex machines like the Turing Machine We’ll use a specific machine and a standard language (grammar) Grep Patterns are a language for a common text Finite State Machine. Pattern Searching.

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RegExp Theory

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  1. RegExp Theory

  2. Finite State Machines

  3. What is a FSM? • Used in CS theory classes • Learned before more complex machines like the Turing Machine • We’ll use a specific machine and a standard language (grammar) • Grep Patterns are a language for a common text Finite State Machine

  4. Pattern Searching

  5. Search 4 a String • fjdklswmcpgtwbvkgfksdsopkdmebcipwmzniugmcttcsctwbvcvoppqmzlgfdwhncishhadsjwbaozhjakwoiatqva • find “sct” in the string the above text • think about how you looked for it

  6. Example Pattern Match C T T Input we are searching in: C C T C S C T S Searching for:

  7. Example Pattern Match C Machine State Position in the input T T C C T C S C T S Searching for: Input we are searching in

  8. Example Pattern Match C Machine State Position in the input T T C C T C S C T S Searching for: Input we are searching in

  9. Example Pattern Match C T T C C T C S C T S Searching for: Input we are searching in

  10. Example Pattern Match C T T C C T C S C T S Searching for: Input we are searching in

  11. Example Pattern Match C T T C C T C S C T S Searching for: Input we are searching in

  12. Example Pattern Match T C C T C S C T S Searching for: Input we are searching in

  13. Example Pattern Match C C T C S C T S Searching for: Input we are searching in A Match was found

  14. Vague Searches • Search multiple times • repeat the process X times • Wildcard / Variable • Find: *, Any_Shape • How do you write this down in a concise way?

  15. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  16. Example Pattern Match Searching for: ANY Input we are searching in

  17. Example Pattern Match Searching for: ANY Input we are searching in NOPE

  18. Example Pattern Match Searching for: ANY Input we are searching in

  19. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  20. Example Pattern Match Searching for: ANY Input we are searching in NO match

  21. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  22. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  23. Example Pattern Match Searching for: ANY Input we are searching in No MATCH

  24. Example Pattern Match Searching for: ANY Input we are searching in

  25. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  26. Example Pattern Match Searching for: ANY Input we are searching in No MATCH

  27. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  28. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  29. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH

  30. Example Pattern Match Searching for: ANY Input we are searching in Shape MATCH! WE FOUND IT

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