Sun שיטת הגמל: "isodd" "is_odd" Sun. תוכנה 1 בשפת Java אוניברסיטת תל אביב

Transcription

1 Java 1

2 2 (24 pages) Sun "isodd" "is_odd" שיטת הגמל: Sun

3 3 Indentation if (condition) if (condition) { { statements; statements; Sun C

4 4 Window->preferences->java->code style->formatter

5 5 Scheme תכנות פונקציונאלי Java תכנות פרוצדוראלי או אימפרטיבי

6 6 1, 1, 2, 3, 5, 8, 13, 21, 34, a 0 = 1 a 1 = 1 a n = a n-1 + a n-2

7 7 package il.ac.tau.cs.software1.recitation3; public class Fibonacci {... /** * Returns the n-th Fibonacci element n >= 0, n is non-negative */ static int computeelement(int n) { if (n == 0) return 1; if (n == 1) return 1; return computeelement(n-1)+computeelement(n-2); else return

8 8 package domain static int

9 9 if else package il.ac.tau.cs.software1.recitation3; public class Fibonacci {... /** * Returns the n-th Fibonacci element n >= 0, n is non-negative */ static int computeelement(int n) { if (n == 0) { return 1; else { if (n == 1) { return 1; else { return computeelement(n-1)+computeelement(n-2);

10 else if package il.ac.tau.cs.software1.recitation3; public class Fibonacci {... /** * Returns the n-th Fibonacci element n >= 0, n is non-negative */ static int computeelement(int n) { if (n == 0) { return 1; else if (n == 1) { return 1; else { return computeelement(n-1)+computeelement(n-2); else if 0 1

11 package il.ac.tau.cs.software1.recitation3; public class Fibonacci {... /** * Returns the n-th Fibonacci element n >= 0, n is non-negative */ static int computeelement(int n) { if ((n == 0) (n == 1 )) { return 1; else { return computeelement(n-1)+computeelement(n-2); 1 1

12 C ((n == 0) (n == 1)) (n==0 n==1) 2 1

13 switch package il.ac.tau.cs.software1.recitation3; public class Fibonacci {... /** * Returns the n-th Fibonacci element n >= 0, n is non-negative */ static int computeelement(int n) { switch(n) { case 0: return 1; case 1: return 1; default: return computeelement(n-1) + computeelement(n-2); 3 1

14 else if default switch break switch case break 4 1

15 switch package il.ac.tau.cs.software1.recitaton3; public class Fibonacci {... /** * Returns the n-th Fibonacci element n >= 0, n is non-negative */ Dead code static int computeelement(int n) { switch(n) { case 0: case 1: return 1; break; default: return computeelement (n-1)+computeelement (n-2); 5 1

16 n computeelement n printnelements computeelement 6 1

17 n package il.ac.tau.cs.software1.recitation3; public class Fibonacci { public static void main(string[] args) { printnelements(10); /** * Prints the first n elements in Fibonacci series n >= 1, n is positive */ static void printnelements(int n) { for(int i = 0; i < n; i++) System.out.println(computeElement(i));... static int computeelement(int n) {... n 7 1

18 for i i main entry point 8 1

19 computeelement 9 1

20 /** * Returns the n-th Fibonacci element */ static int computeelement(int n) { if (n==0 n==1) return 1; int prev = 1; int prevprev = 1; int curr; for (int i = 2; i < n; i++) { curr = prev + prevprev; prevprev = prev; prev = curr; curr = prev + prevprev; return curr; 0 2

21 prevprev curr, prev computeelement (curr prevprev (KISS principle) prev 1 2

22 :computeelement n static void printnelements(int n) { for(int i=0; i<n; i++) System.out.println(computeElement(i)); printnelements for computeelement scheme memoization 2 2

23 memoization 3 2

24 for vs. while while Java while for printnelements static void printnelements(int n) { for(int i = 0 ; i < n ; i++) System.out.println(computeElement(i)); static void printnelements(int n) { int i = 0; while (i < n) { System.out.println(computeElement(i)); i++; 4 2

25 while vs. do while n >= 1, n is positive */ static void printnelements(int n) { int i = 0; while(i < n) { System.out.println(computeElement(i)); i++; n >= 1, n is positive */ static void printnelements(int n) { int i = 0; do { System.out.println(computeElement(i)); i++; while (i < n); n>1 5 2

26 26