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CGS – 4854 Summer 2012

CGS – 4854 Summer 2012 . Instructor: Francisco R. Ortega Chapter 5 Regular Expressions. Web Site Construction and Management. Today’s Lecture. Chapter 5 Regular Expressions Talk about tutorial 4 and homework 4 Help with homework #4. Mid-Term. Mid-Term June 21 st .

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CGS – 4854 Summer 2012

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  1. CGS – 4854 Summer 2012 Instructor: Francisco R. Ortega Chapter 5 Regular Expressions Web Site Construction and Management

  2. Today’s Lecture • Chapter 5 Regular Expressions • Talk about tutorial 4 and homework 4 • Help with homework #4

  3. Mid-Term • Mid-Term June 21st. • Chapters 1,2,3 and 4. • Possible review for mid-term • June 14 (after quiz 4) or June 19 • Extra Credit for Mid-Term • Extra credit question may be Java related or Regular Expressions (if covered before the exam) • You are allowed to bring one letter size paper to the exam

  4. ASCII Table (Part 1)

  5. Regular Expressions • Match strings of text (wiki) • Sequence of regular expressions is known as a pattern • Regular expressions contain • Wildcards • Special characters • Escape sequences

  6. Regular Expressions 101 • Characters match themselves except: [\^$.|?*+() • \ suppresses the meaning of special characters • [] starts a character class. We match one from the class. • - specifies a range of characters • ^ negates a character class • . matches any single character except line break • | matches either the left, or the right (or)

  7. Character Classes • [xyz] : will match x or y or z • [a-z] : will match lowercase letters • [a-zA-Z] : will match all letters • [a-Z] :will not match any letters (why?) • [A-z] : will match all letters but additional symbols. Why? • [^abc] : Any character except for a,b or c.

  8. Predefined classes

  9. Escape Sequence • \. : would match a period • [.] : would match a period • \ does not lose special meaning inside square brackets [\d]

  10. Alternation • yes|no • yes|no|maybe • It will match either yes,no or maybae. • But only one of them.

  11. Grouping and Capturing • (pattern) • Capturing pattern. • Can retrieve values from \1 thru \9 • Example • Text: abyes3 • [a-z] ([a-z]) (yes|no) \d • \1 is equal to b • \2 is equal to yes • (?:pattern) • Only used for grouping

  12. Ignoring case • (?i)yes|no • [yY] [eE] [sS] | [Nn] [Oo]

  13. Repetition

  14. Regex in java • You will need to use two backslashes • Regex: \d • Java regex: “\\d”

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