CSE240 Lecture 21

Introduction to Programming Languages
Lists in LISP
(202011)

Transcript

1. jgs CSE 240 Introduction to Programming Languages Lecture 21: Lists in LISP Dr. Javier Gonzalez-Sanchez javiergs@asu.edu javiergs.engineering.asu.edu | javiergs.com PERALTA 230U Office Hours: By appointment
2. jgs Midterm Exams
3. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 3 jgs Part 1 / 13 1. Spragg, Hunter 2. Vaidya, Yogesh 3. Donta, Nipoon Naresh 4. Li, Zhuoran 5. Vega, Moses
4. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 4 jgs Part 2 / 13 1. Seo, Jinha 2. Wallace, Dallin 3. Esan, Oluwamayowa 4. Karimi, Mohammad 5. Anubrolu, Charishma
5. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 5 jgs Part 3 / 13 1. Annison, Madeline 2. Heinemann, James 3. Shaw, Ethan 4. Crandall, Gabriel 5. Sandy, David
6. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 6 jgs Part 4 / 13 1. Modi, Dhruvi Jayeshkumar 2. NolastName, Maaz Ahmed 3. Shaikh, Ariyan 4. Desai, Keyur 5. Lopez, Maximiliano
7. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 7 jgs Part 5 / 13 1. Ozturk, Alper 2. Osif, Cecil 3. Thota, Supreeth Yadav 4. Chen, Shengdong 5. Meacham, Gabrielle
8. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 8 jgs Part 6 / 13 1. Yadav, Rajat 2. Fishco, Harrison 3. Alzara, Ibrahim Mohammed I 4. Jain, Vishesh Nirmal 5. Buice, Robert
9. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 9 jgs Part 7 / 13 1. Sullivan, Nathaniel 2. Ortega, Gabriel 3. Vance, Tyler 4. Archer, Anthony 5. Baney, Broc
10. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 10 jgs Part 8 / 13 1. Carson, Austin 2. Whitehouse, Chase 3. Mckinney, Kyle 4. Robertson, Hannah 5. Stuva, Brayden
11. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 11 jgs Part 9 / 13 1. Braunschweig, Jackson 2. Cerny, Trenton 3. Obrien, Sophie 4. Sanchez, Derek 5. Bhattacharya, Anand
12. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 12 jgs Part 10 / 13 1. Grabowski, Mateusz 2. Bergeson, Donald 3. Schwartz, Jeremiah 4. Masetty, Abhishek 5. Ummadisingu, Gnana Chaitanya
13. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 13 jgs Part 11 / 13 1. Lofgreen, Blake 2. Perez, Victor Ledezma 3. Guthy, Pavitra 4. Lin, Allen 5. Thompson, Trevor
14. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 14 jgs Part 12 / 13 1. Edsitty, Robyn 2. Kakarla, Hethesh 3. Mcmahon, Taylor 4. Gonzalez, Cristian Munoz 5. Nguyen, Kevin
15. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 15 jgs Part 13 / 13 1. Alaklabi, Faisal 2. Plitzuweit, Zachary 3. Hagh, David 4. Chepyala, Alekhya 5. Sabri, Hamza
16. jgs Previously Atomic Expressions
17. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 17 jgs Everything is a List § (+ 27/32 32/57) 2563/1824 § (* 2.342 3.2e4) 74944.0 § (* 2.342 9.212 -9.23 3/4) ; You can mix number types -149.34949 § (/ 3 5) ; The return type stays as general as possible 3/5 § (/ 3.0 5) ;Here LISP had no choice: convert to a float 0.6 § (1+ 3) 4
18. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 18 jgs Everything is a List § (string-upcase "How about that!") "HOW ABOUT THAT!" § (reverse "Four score and seven years ago") "oga sraey neves dna erocs ruoF" § (length "Four score and seven years ago") 30 § (sqrt 2) 1.4142135 § (sqrt -1.0) #C(0 1.0) § (SqRt -1.0) ;LISP symbols are case-insensitive #C(0 1.0)
19. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 19 jgs Function Arguments § Some functions have NOT a fixed number of arguments: (+ 100 231 201 921 221 231 -23 12 -34 134) § Some functions have a fixed number of arguments and optional arguments: (subseq "Four score and seven years ago" 9) "e and seven years ago” (subseq "Four score and seven years ago" 9 23) "e and seven ye"
20. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 20 jgs Predicates (boolean functions) § LISP has a special name for functions which return "true" (usually t) or "false" (nil). These functions are called predicates. • (= 4 3) ; is 4 == 3 ? NIL • (< 3 9) ; is 3 < 9 ? T • (numberp "hello") ; is "foo" a number? NIL • (oddp 9) ; is 9 an odd number? T
21. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 21 jgs Errors § Errors stop the program execution • (/ 1 0) *** - division by zero • (blah-blah-blah 1 0 "foo") *** - EVAL: the function BLAH-BLAH-BLAH is undefined
22. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 22 jgs Recursion § When a list contains another list among its expressions, the evaluation procedure is recursive. • (+ 33 (* 2.3 4) 9) 51.2 • (+ (length "Hello World") 44) 55 • (* (+ 3 2.3) (/ 3 (- 9 4))) ;in C++: (3+2.3) * (3 / (9-4)) 3.1800003 • (log (log (log 234231232234234123))) 1.3052895 • (+ (* (sin 0.3) (sin 0.3)) ; expressions may use multiple lines (* (cos 0.3) (cos 0.3))) ; sin(0.3)^2 + cos(0.3)^2 1.0000001 ; = 1. Rounding inaccuracy
23. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 23 jgs Recursion § (and (< 3 (* 2 5)) (not (>= 2 6))) ; (3 < 2 * 5) && !(2 >= 6) T § (print (+ 2 3 4 1)) 10 10 § (+ (* 2 3) (/ 3 2) 9) 33/2
24. jgs Control Structures
25. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 25 jgs Control Structures § There are some evaluable lists which are not functions. § These lists are known as macros or special forms. § The control structure if is a special form.
26. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 26 jgs Control Structures § (if (<= 3 2) (* 3 9) (+ 4 2 3)) ; if (3<=2) {return 3*9;} else {return 4+2+3;} 9 § (if (> 2 3) 9) ; if (2>3) {return 9;} else {return nil} NIL § (if (= 2 2) (if (> 3 2) 4 6) 9) 4 § (+ 4 (if (= 2 2) (* 9 2) 7) ) 22
27. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 27 jgs Control Structures § if only allows one test-expression, one then-expression, and one optional- else-expression. § To do more things in the then-expression we need to make a block. Blocks are made with the special form progn, which takes the form: (progn expr1 expr2 expr3 ...) • (if (> 3 2) (progn (print "hello") (print "yo") (print "whassup?") (+ 2 2)) (+ 1 2 3)) "hello" "yo" "whatsup?" 4
28. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 28 jgs Questions
29. jgs CSE 240 Introduction to Programming Languages Javier Gonzalez-Sanchez, Ph.D. javiergs@asu.edu Fall 2021 Copyright. These slides can only be used as study material for the class CSE240 at Arizona State University. They cannot be distributed or used for another purpose.