do/while Structure (L15) * do/while structure * break Statement * continue Statement * Loop Programming Techniques - Interactive input within a loop - Selection within a loop - Evaluating functions of one variable - Interactive loop control * Exercise/Home Work Dr. Ming Zhang

General Form of do/while Statement do statement(s); while (condition expression); The process continues until the condition expression evaluates to zero ( false) Dr. Ming Zhang

Flowchart of do/while Structure Enter do/while statement Execute the statement(s) after do exit the Loop false do Evaluate the statement expression true Dr. Ming Zhang

Example of do/while #include using std::cout; int main( ) { int counter = 1; do { cout << counter << “ “; } while (++counter <=10); return(0); } output: Dr. Ming Zhang

break Statement * The break statement, when executed in a while, for, do/while, or switch structure, causes immediate exit for that structure. * Program execution continues with the first statement after the structure. * Common uses of the break statement are to escape early from a loop, or to skip the remainder of a switch structure Dr. Ming Zhang

Example of break Statement #include using std::cout; int main( ) { int x; for ( x=1; x<=10; x++) { if ( x ==5) break; //broke out of loop at x of 5 cout << x << “ “; } return(0); } Output: Dr. Ming Zhang

Continue Statement * The continue statement, when executed in a while, for, or do/while structure, skips the remaining statements in the body of that structure, and proceeds with the next iteration of the loop. * In while and do/while structures, the loop- continuation test is evaluated immediately after the continue statement is executed. * In the for structure, the increment expression is executed, then the loop-continuation test is evaluated. Dr. Ming Zhang

Example of continue Statement #include using std::cout; int main( ) { int x=1; while ( x <=10) { if ( x ==5) //skip remaining code in continue; //loop only if x is 5 cout << x << “ “; x=x+1; } return(0);} Output: ??????????????????? Dr. Ming Zhang

Example of continue Statement #include using std::cout; int main( ) { int x=1; while ( x <=10) { if ( x ==5) //skip remaining code in continue; //loop only if x is 5 cout << x << “ “; x=x+1; } return(0);} Output: …… infinite loop Dr. Ming Zhang

Example of continue Statement #include using std::cout; int main( ) { int x=0; while ( ++x <=10) { if ( x ==5) //skip remaining code in continue; //loop only if x is 5 cout << x << “ “; } return(0);} Output: Dr. Ming Zhang

Example of continue Statement #include using std::cout; int main( ) { int x; for ( x=1; x<=10; x++) { if ( x ==5) //skip remaining code in continue; //loop only if x is 5 cout << x << “ “; } return(0); } Output: ???????????????? Dr. Ming Zhang

Example of continue Statement #include using std::cout; int main( ) { int x; for ( x=1; x<=10; x++) { if ( x ==5) //skip remaining code in continue; //loop only if x is 5 cout << x << “ “; } return(0); } Output: Dr. Ming Zhang

Interactive Input within a Loop #include #define MAX 5 using std::cout; using std::cin; int main( ) {int count, num; float total, average; for(total=0.0,count=1;count<=MAX;++count) { cout << “Enter a number:”; cin >> num; total = total + num;} average = total/MAX; cout << “ The average is” << average<<endl; return(0);} Dr. Ming Zhang

Selection within a Loop #include #define MAX 5 #define THR 8 using std::cout; using std::cin; int main( ) {int count, num; float total, average; for(total=0.0,count=1;count<=MAX;++count) { cout > num; if(num> THR) total = total + num; else total = total - num;} average = total/MAX; cout << “ The average is” << average<<endl; return(0);} Dr. Ming Zhang

Evaluating Functions of One Variable # include using std::cout; using std::endl; int main( ) { int x, y; for (x=2; x<=6; ++x){ y =10*x*x +3*x -2; //function of one variable cout << x << y<<endl; } return(0); } Dr. Ming Zhang

Interactive Loop Control #include using std::cout; using std::endl; int main( ) { int num, final; cout <<“Enter the final number for the table:” cin << final;//variable final used to control a loop for(num = 1; num <= final; ++num) cout << num << (num*num); return(0) } Dr. Ming Zhang

Common Programming Error (15_1) # include using std::cout; using std::endl; int main( ) { int x, y; for (x=2; x<=1; ++x){ y =10*x*x +3*x -2; cout << x << y<<endl;} return(0);} ERROR Dr. Ming Zhang

Common Programming Error (15_2) # include using std::cout; using std::endl; int main( ) { int x, y; for (x=2, x<=1, ++x){ y =10*x*x +3*x -2; cout << x << y<<endl;} return(0);} ERROR Dr. Ming Zhang

Common Programming Error (15_3) # include using std::cout; using std::endl; int main( ) { int x, y; for (x=2;x<=1; ++x); { y =10*x*x +3*x -2; cout << x << y<<endl;} return(0);} ERROR Dr. Ming Zhang

Common Programming Error (15_4) int num1 = 10, num2 = 10; cin >> opselect ; switch (opselect) { case 1: cout << “The sum:”<< (num1+num2); case 2: cout<<“The product”<<(num1*num2); break; case 3: cout<<“The division”<<(num1/num2); break; } ERROR Dr. Ming Zhang

Common Programming Error (15_5) int num1 = 10, num2 = 10; cin >> opselect ; switch (opselect) { case1: cout << “The sum:”<< (num1+num2); break; case2: cout<<“The product”<<(num1*num2); break; case3: cout<<“The division”<<(num1/num2); break; } ERROR Dr. Ming Zhang

Common Programming Error (15_6) int num1 = 10, num2 = 10; cin >> opselect ; switch (opselect) { case 1: cout << “The sum:”<< (num1+num2); break; case 1: cout<<“The product”<<(num1*num2); break; case 1: cout<<“The division”<<(num1/num2); break; } ERROR Dr. Ming Zhang