Thursday, December 21, 2006 The Briggs/Chase Law of Program Development: To determine how long it will take to write and debug a program, take your best estimate, multiply that by two, add one, and convert to the next higher units To determine how long it will take to write and debug a program, take your best estimate, multiply that by two, add one, and convert to the next higher units.

§Friday classes §Assignment 1 on website §Late Assignment Policy §Quiz 1 has been marked

Fibonacci numbers F1=1 F2=2 Fn=Fn-1 + Fn …

int i; double Fn, Fnminus2=1, Fnminus1=2; for (i=0; i<100; i++){ Fn=Fnminus1 + Fnminus2; cout<<Fn<<" "; //updating values below Fnminus2=Fnminus1; Fnminus1=Fn; }

The for loop int main() { int x; for(x=0; x != 123; ) { cout << "Enter a number: "; cin >> x; } return 0; }

The for loop int x = 0; for( ; x<10; ) { cout << x << " " ; ++x; } int x; for (x=0; x<10; x++) { cout << x << " " ; }

for loop Self test exercise: Write a function to calculate the factorial of a number. 4! = 24 5! = 120 6! = 720 7! =5040 8!=40320

Print 30 stars on the screen ******************************

Print 30 stars on the screen int i; for (i=0; i<30; i++) { cout<<"*"; } cout<<endl;

Print 20 lines of 30 stars on screen ******************************

Print 20 lines of 30 stars on screen int i,j; for (j=0; j<20; j++) { for(i=0; i<30; i++) { cout<<"*"; } cout<<endl; } cout<<endl;

Nested Loops int main() { int i, j; for(i=0; i<3; i++) { for(j=0; j <= 4; j++) cout<<“The value of i=” <<i<<“ and j= ”<<j<<“\n”; cout<<"Out of the inner for-loop\n"; } return 0; }

Nested Loops The value of i=0 and j=0 The value of i=0 and j=1 The value of i=0 and j=2 The value of i=0 and j=3 The value of i=0 and j=4 Out of the inner for-loop The value of i=1 and j=0 The value of i=1 and j=1 The value of i=1 and j=2 The value of i=1 and j=3 The value of i=1 and j=4 Out of the inner for-loop The value of i=2 and j=0 The value of i=2 and j=1 The value of i=2 and j=2 The value of i=2 and j=3 The value of i=2 and j=4 Out of the inner for-loop

Print this pattern on screen * ** *** **** ***** ****** ******* ******** ********* ********** *********** ************ ************* ************** *************** **************** ***************** ****************** ******************* ********************

Print this pattern on screen int i,j; for (j=0; j<20; j++) { for(i=0; i<(j+1); i++) { cout<<"*"; } cout<<endl; } cout<<endl;

SELF TEST: Print this pattern on screen ******************** ******************* ****************** ***************** **************** *************** ************** ************* ************ *********** ********** ********* ******** ******* ****** ***** **** *** ** *

Do-while loops  Do-while loops are very much like while loops, except  that the loop body is executed once before the loop condition is ever evaluated.  After that, they are exactly the same.

Do-while loops  Example: do { cout << "This is a test"; } while (0); –Compare this to: while (0) { cout << "This is a test"; }

char ans; do { cout << "Hello\n"; cout << "Do you want another greeting?\n" << "Press y for yes, n for no,\n" << "and then press return: "; cin >> ans; } while (ans == 'y' || ans == 'Y'); cout << "Good-Bye\n";

int secret=3, guess; char answer; do { cout<<"Guess a number between 0 and 10 "; cin>>guess; if (guess < secret) cout<<"Sorry, Too Small!"<<endl; else if (guess > secret) cout<<"Sorry, Too Big!"<<endl; else cout<<"Congratulations! Your guess is right!"<<endl; cout<<"Do you want to play again?\n"; cin>>answer; }while(answer=='y' || answer=='Y');

int secret=3, guess; char answer; do { cout<<"Guess a number between 0 and 10 "; cin>>guess; while((guess 10)) { cout<<"Out of range. Enter number between 0 and 10"; cin>>guess; } if (guess < 3) cout<<"Sorry, Too Small!"<<endl; else if (guess > 3) cout<<"Sorry, Too Big!"<<endl; else cout<<"Congratulations! Your guess is right!"<<endl; cout<<"Do you want to play again?\n"; cin>>answer; }while(answer=='y' || answer=='Y');

continue statement int i; for (i=0; i<50; i++){ if ((i==4)||(i==42)) continue; cout<<i<<"\n"; } In for-loop a continue statement will cause the increment part to be performed and then conditional expression to be executed.

break statement int i, j=15; for (i=0; i<50; i++){ if((i*2)==(j+3)) break; else { cout<<i<<" "; }

break statement int i, j=15; for (i=0; i<50; i++){ if((i*2)==(j+3)) break; else { cout<<i<<" "; } //prints

continue int main() { int x; for(x=0; x<=10; x++) { if(x%2) continue; cout << x << " "; } return 0; } //output?

continue int main() { int x; for(x=0; x<=10; x++) { if(x%2) continue; cout << x << " " ; } return 0; } //output?

Self Test: continue int loop ; for( loop=2; loop<10; ++loop ) {if (loop%3==0) continue; cout << loop << " "; } cout<<loop<<endl; int loop ; for( loop=2; loop<10; ++loop ) {if (loop%3) continue; cout << loop << " "; } cout<<loop<<endl;

Self Test: continue What happens here? int i, s=0 ; for( i=1; i<5; ) { continue; cout<<i<<endl; }

Self Test: continue int i=0; while (i<10){ i++; if (i==5) continue; cout<<i; }

Self Test: break break forces immediate exit from loop int main() { int t; // what is the output? for (t=0; t<100; t++) { if(t==10) break; cout << t << “ “; } return 0; }

break int i; for( i=1; ; ++i ) {if (i==5) continue; if (i%9 ==0) break; cout<<i; } cout<<"\n"<<i;

break int i; for( i=1; ; ++i ) {if (i==5) continue; if (i%9 ==0) break; cout<<i; } cout<<"\n"<<i; //prints

§continue and break inside loops only.

char a,b; cin>>a>>b; cout<<a<<b<<endl; cout<<a<<" "<<b<<endl;