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
   

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2. jgs
   Midterm Exams
   

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3. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 3
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   Part 1 / 13
   1. Spragg, Hunter
   2. Vaidya, Yogesh
   3. Donta, Nipoon Naresh
   4. Li, Zhuoran
   5. Vega, Moses
   

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4. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 4
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   Part 2 / 13
   1. Seo, Jinha
   2. Wallace, Dallin
   3. Esan, Oluwamayowa
   4. Karimi, Mohammad
   5. Anubrolu, Charishma
   

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5. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 5
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   Part 3 / 13
   1. Annison, Madeline
   2. Heinemann, James
   3. Shaw, Ethan
   4. Crandall, Gabriel
   5. Sandy, David
   

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6. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 6
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   Part 4 / 13
   1. Modi, Dhruvi Jayeshkumar
   2. NolastName, Maaz Ahmed
   3. Shaikh, Ariyan
   4. Desai, Keyur
   5. Lopez, Maximiliano
   

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7. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 7
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   Part 5 / 13
   1. Ozturk, Alper
   2. Osif, Cecil
   3. Thota, Supreeth Yadav
   4. Chen, Shengdong
   5. Meacham, Gabrielle
   

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8. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 8
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   Part 6 / 13
   1. Yadav, Rajat
   2. Fishco, Harrison
   3. Alzara, Ibrahim Mohammed I
   4. Jain, Vishesh Nirmal
   5. Buice, Robert
   

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9. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 9
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   Part 7 / 13
   1. Sullivan, Nathaniel
   2. Ortega, Gabriel
   3. Vance, Tyler
   4. Archer, Anthony
   5. Baney, Broc
   

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10. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 10
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    Part 8 / 13
    1. Carson, Austin
    2. Whitehouse, Chase
    3. Mckinney, Kyle
    4. Robertson, Hannah
    5. Stuva, Brayden
    

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11. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 11
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    Part 9 / 13
    1. Braunschweig, Jackson
    2. Cerny, Trenton
    3. Obrien, Sophie
    4. Sanchez, Derek
    5. Bhattacharya, Anand
    

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12. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 12
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    Part 10 / 13
    1. Grabowski, Mateusz
    2. Bergeson, Donald
    3. Schwartz, Jeremiah
    4. Masetty, Abhishek
    5. Ummadisingu, Gnana Chaitanya
    

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13. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 13
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    Part 11 / 13
    1. Lofgreen, Blake
    2. Perez, Victor Ledezma
    3. Guthy, Pavitra
    4. Lin, Allen
    5. Thompson, Trevor
    

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14. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 14
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    Part 12 / 13
    1. Edsitty, Robyn
    2. Kakarla, Hethesh
    3. Mcmahon, Taylor
    4. Gonzalez, Cristian Munoz
    5. Nguyen, Kevin
    

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15. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 15
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    Part 13 / 13
    1. Alaklabi, Faisal
    2. Plitzuweit, Zachary
    3. Hagh, David
    4. Chepyala, Alekhya
    5. Sabri, Hamza
    

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    Previously
    Atomic Expressions
    

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17. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 17
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    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
    

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18. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 18
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    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)
    

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19. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 19
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    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"
    

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20. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 20
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    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
    

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21. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 21
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    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
    

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22. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 22
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    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
    

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23. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 23
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    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
    

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    Control Structures
    

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25. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 25
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    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.
    

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26. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 26
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    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
    

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27. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 27
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    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
    

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28. Javier Gonzalez-Sanchez | CSE240 | Spring 2020 | 28
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    Questions
    

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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.
    

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