UP Lecture 05

Compilers
Regular Expressions
(202402)

Transcript

1. jgs Compilers Lecture 05: Regular Expressions Dr. Javier Gonzalez-Sanchez jgonzalezs@up.edu.mx
2. Dr. Javier Gonzalez-Sanchez | Compilers | 2 jgs
3. jgs Previously …
4. Dr. Javier Gonzalez-Sanchez | Compilers | 4 jgs Keywords Lexical Alphabet Symbol String Word Token Rules Regular Expression Deterministic Finite Automata
5. Dr. Javier Gonzalez-Sanchez | Compilers | 5 jgs Key Ideas Lexical Alphabet Symbol String Word Token Rules Regular Expression Deterministic Finite Automata
6. Dr. Javier Gonzalez-Sanchez | Compilers | 6 jgs Homework Programming Assignment #1 Develop a Lexical Analyzer by coding a DFA
7. Dr. Javier Gonzalez-Sanchez | Compilers | 7 jgs Key Ideas Lexical Alphabet Symbol String Word Token Rules Regular Expression Deterministic Finite Automata
8. jgs Regular Expression
9. Dr. Javier Gonzalez-Sanchez | Compilers | 9 jgs Regular expression § A rule to describe finite combinations of symbols (sequences) that are considered well-formed. § Regular expression has symbols and operators. § Symbols are defined in the alphabet. § The operators used in regular expressions are: § * (0 or more), § + (1 or more), § ? (0 or 1), § | (or). § [ ] to enclose sets of symbols without enumerating all of them, such as [0- 9] or [A-Z]. § Parenthesis.
10. Dr. Javier Gonzalez-Sanchez | Compilers | 10 jgs Regular expression | Examples Token Regular Expression (rule) Examples (words) foobarOne (a | b) {a, b} foobarTwo (a | b)(a | b) {aa, bb, ba, ab} foobarThree a* { , a, aa, aaa, aaaa, ... } foobarFour (a | b)* { , a, b, aa, bb, ...abba ...} foobarFive a+ { a, aa, aaa, aaaa, ... } foobarSix [a-z]+ {hello, world, etc, …} number [0-9]+ {1934, 0101, 33, 12321…}
11. Dr. Javier Gonzalez-Sanchez | Compilers | 11 jgs Regular expression | Examples * These definitions are NOT fully complete or correct. The purpose is only to exemplify RE. For instance, 07 matches as an integer, which will NOT be the case for our language. Token1 Regular Expression (rule) Example (word) digit 0 | 1 | 2 | 3 | ... | 9 3 integer digit+ 1945 fraction .digit+ .55 exponent e(+|-)?digit+ e+210 floatDraftOne integer(fraction?) (exponent?) 340.08e-14 floatDraftTwo {[-+]?([0-9]+\.?[0-9]*|\.[0-9]+)([eE][-+]?[0- 9]+)?} binary 0b(0|1)+ 0b1010
12. Dr. Javier Gonzalez-Sanchez | Compilers | 12 jgs Regular expression | Operators
13. jgs Additional Examples
14. Dr. Javier Gonzalez-Sanchez | Compilers | 14 jgs Handwritten notes Regular expression Regular expression Regular expression
15. Dr. Javier Gonzalez-Sanchez | Compilers | 15 jgs Handwritten notes Regular expression Regular expression -9
16. Dr. Javier Gonzalez-Sanchez | Compilers | 16 jgs Handwritten notes Is this correct? Is this correct? Is this correct?
17. Dr. Javier Gonzalez-Sanchez | Compilers | 17 jgs Handwritten notes Error Correct
18. jgs Test Yourselves
19. Dr. Javier Gonzalez-Sanchez | Compilers | 19 jgs Regular expressions - Examples Define a regular expression for each case a) URLs a) Email addresses a) ZIP codes
20. Dr. Javier Gonzalez-Sanchez | Compilers | 20 jgs DFA- Examples Define a DFA for each case a) URLs a) Email addresses a) ZIP codes
21. Dr. Javier Gonzalez-Sanchez | Compilers | 21 jgs Let’s Work
22. Dr. Javier Gonzalez-Sanchez | Compilers | 22 jgs Questions
23. jgs Compilers Javier Gonzalez-Sanchez, Ph.D. jgonzalezs@up.edu.mx Spring 2024 Copyright. These slides can only be used as study material for the Compilers course at Universidad Panamericana. They cannot be distributed or used for another purpose.