Control Structures: Iteration

• The do-while statement
• Syntax: do { statements } while (expression);
• Statements in the block are executed iteratively while expression is true. The expression is evaluated at the end of each iteration. The block of statements is guaranteed to be executed at least once
• Example of a do-while loop


• The while statement
• Syntax:
  while (expression){ statements }
• While expression is true, the statements in the block are excuted iteratively. The expression is evaluated at the end of each iteration
• Example of an infinite loop:
  while(1){ statements }
• Example of a while loop


• The for statement
• Syntax:
  for (expression_1; expression_2; expression_3){ statements }
• Usually is a more compact substitute for the while and do-while loops
• For example the following two loops are equivalent:
  

  int i = 1; while ( i <= n ) { int s += i; i++; }

  for (int i = 1; i <= n; i++) int s += i;

• Any of the expressions can be omitted from the statement, making the following statement valid:
  for ( ; i > 0 ; ){ ... }
• Example of a for loop


• The logical &&, || operators can be used to evaluate multiple expressions in the while and do-while and for loops
• The comma operator can be used to evaluate more than one expression in the loop. For example:
  for ( int i = 0, int j = 1; j > 0; i++){ ...}
• The break statement may be used to break out of a loop
• The continue statement causes a jump to the evaluation of the expression for loop termination
• When two loops are nested, each iteration of the outer loop is accompanied by a complete execution of the inner loop
• Exercises...