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Learning Scheme Programming: Lecture 23, Study notes of Programming Paradigms

University of MontevalloProgramming Paradigms

A part of a university lecture series on scheme programming. It includes announcements, a scheme scheme, quotes about scheme, an introduction to scheme fundamentals, special forms, and a discussion on counting trees and lambda expressions. It also covers pairs and lists, symbolic programming, and scheme lists and quotation.

What you will learn

  • How are pairs and lists used in Scheme?
  • What are the fundamental concepts of Scheme programming?
  • What are special forms in Scheme?

Typology: Study notes

2021/2022

Uploaded on 09/27/2022

laskhminaran
laskhminaran 🇺🇸

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61A Lecture 23
Wednesday, October 30
Announcements
•Homework 7 due Tuesday 11/5 @ 11:59pm.
•Project 1 composition revisions due Thursday 11/7 @ 11:59pm.
•Midterm 2 is graded.
(And yes, it was very challenging.)
Mean: 30
Solutions will be posted and exams distributed soon.
2
Scheme
http://imgs.xkcd.com/comics/lisp_cycles.png
Scheme is a Dialect of Lisp
What are people saying about Lisp?
•"The greatest single programming language ever designed."
-Alan Kay, co-inventor of Smalltalk and OOP
•"The only computer language that is beautiful."
-Neal Stephenson, DeNero's favorite sci-fi author
•"God's programming language."
-Brian Harvey, Berkeley CS instructor extraordinaire
4
Scheme Fundamentals
Scheme programs consist of expressions, which can be:
•Primitive expressions: 2, 3.3, true, +, quotient, ...
•Combinations: (quotient 10 2), (not true), ...
Numbers are self-evaluating; symbols are bound to values.
Call expressions include an operator and 0 or more operands in parentheses.
(Demo)
5
> (quotient 10 2)
5
> (quotient (+ 8 7) 5)
3
> (+ (* 3
(+ (* 2 4)
(+ 3 5)))
(+ (- 10 7)
6))
“quotient” names Scheme’s
built-in integer division
procedure (i.e., function)
Combinations can span
multiple lines
(spacing doesn’t matter)
Special Forms
pf3

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Download Learning Scheme Programming: Lecture 23 and more Study notes Programming Paradigms in PDF only on Docsity!

61A Lecture 23

Wednesday, October 30

Announcements

  • Homework 7 due Tuesday 11/5 @ 11:59pm.
  • Project 1 composition revisions due Thursday 11/7 @ 11:59pm.
  • Midterm 2 is graded.  (^) (And yes, it was very challenging.)  Mean: 30  (^) Solutions will be posted and exams distributed soon. 2

Scheme

http://imgs.xkcd.com/comics/lisp_cycles.png

Scheme is a Dialect of Lisp

What are people saying about Lisp?

  • "The -Alan greatest Kay, co-inventor single programming of Smalltalk language and OOPever designed."
  • "The only computer language that is beautiful." -Neal Stephenson, DeNero's favorite sci-fi author
  • "God's programming language." -Brian Harvey, Berkeley CS instructor extraordinaire 4

Scheme Fundamentals

Scheme programs consist of expressions, which can be:

  • Primitive expressions: 2 , 3.3, true, +, quotient, ...
  • Combinations: (quotient 10 2), (not true), ... Numbers are self-evaluating; symbols are bound to values. Call expressions include an operator and 0 or more operands in parentheses. (Demo) 5

5 (quotient 10 2) (quotient (+ 8 7) 5) (^3) > (+ (* 3 (+ (* (+ 23 4)5))) (+ (- 6)) 10 7) “quotient” built-in integer names Scheme’sdivision procedure (i.e., function) Combinations multiple linescan span (spacing doesn’t matter)

Special Forms

Special Forms

A combination that is not a call expression is a special form :

  • (^) If expression: (if ) - And and or : (and <e 1 > ... ), (or <e 1 > ... ) - Binding symbols: (define ) - New procedures: (define ( ) )

    (define pi 3.14) 6.28 (* pi 2) (define (abs x) (if (< (- xx) 0) x)) 3 (abs -3) The symbol “pi” global is bound frame to 3.14 in the A procedure is symbol created “abs” and bound to the 7 Evaluation : (1) predicate Evaluate expression. the (2) Evaluate either the alternative. consequent or (Demo)

Counting Trees

Example: Counting Binary Trees

so many trees exist 9 a long noun phrase a two word modifier some trees are balanced the other trees lean The structure of a sentence can be described by a tree. Each sub-tree is a constituent. W X Y Z (Demo) The number of trees over n leaves with k leaves in the left and n-k in the right is: (The number of trees with k leaves) * (The number of trees with n-k leaves)

Lambda Expressions

Lambda Expressions

Lambda expressions evaluate to anonymous procedures.

(lambda (<formal-parameters>) ) Two equivalent expressions: (define (plus4 x) (+ x 4)) (define plus4 (lambda (x) (+ x 4))) An operator can be a call expression too: ((lambda (x y z) (+ x y (square z))) 1 2 3) add-^ Evaluates x -&- y -&- z^^2 toprocedure^ the 11

Pairs and Lists