Adobe 38043740 Developing Applications - Page 123

DEVELOPING COLDFUSION 9 APPLICATIONS 118 The CFML Programming Language The example also shows two issues with index arithmetic: in this form of loop you must make sure to initialize the index, and keep track of where the index is incremented. In this case, because the index is incremented at the top of the loop, initialize it to 0 so it becomes 1 in the first loop. Using while loops The while loop has the following format: while (expression) statement The while statement does the following: 1 Evaluates the expression. 2 If the expression is True, it does the following: a Executes the statement, which can be a single semicolon-terminated statement or a statement block in curly brackets. b Returns to step 1. If the expression is False, processing continues with the next statement. The following example uses a while loop to populate a 10-element array with multiples of five. a = ArrayNew(1); loop = 1; while (loop LE 10) { a[loop] = loop * 5; loop = loop + 1; } As with other loops, make sure that at some point the whileexpression is False and be careful to check your index arithmetic. Using do-while loops The do-while loop is like a while loop, except that it tests the loop condition after executing the loop statement block. The do-while loop has the following format: do statement while (expression); The dowhile statement does the following: 1 Executes the statement, which can be a single semicolon-terminated statement or a statement block in curly brackets. 2 Evaluates the expression. 3 If the expression is true, it returns to step 1. If the expression is False, processing continues with the next statement. The following example, like the while loop example, populates a 10-element array with multiples of 5: a = ArrayNew(1); loop = 1; do { a[loop] = loop * 5; loop = loop + 1; } while (loop LE 10); Last updated 1/20/2012