ASP control structure BRANCHING STATEMENTS Branching statements perform

ASP control structure BRANCHING STATEMENTS Branching statements perform a test. They might check to see if x=2 or y=5 or if x>y. Based upon the results of the test, certain code is executed while other code is skipped. There are two types of branching statements we will run into: If--Then--Else is generally used to choose from one of two sets of lines to execute. EXAMPLE: If int. Friends > 5 then Response. Write "You have a lot of friends" Else Response. Write "You need to be more social. " End If As you can see from above, there are four parts to the If--Then statement. An expression that is either true or false An "if true" section An "if false" section (OPTIONAL) An ending statement

Branching Structure • Basic If--Then Rules: • Every expression tested will either evaluate to true or false • You can only use one statement in the single line if--then • If you use more than one line, you must use End If • If you want action in the case of a false evaluation, you must use the else statement • Once an expression evaluates to true, the If/Then structure is exited. Example

Select case • • SELECT CASE Although you can use the Else. If statement to check multiple expressions, you should really use the Select Case branching control structure when that situation arises. Select Case str. Language Case "Spanish" Response. Write "Ola" Case "English" Response. Write "Hello" Case "French" Response. Write "Bonjour" Case "German" Response. Write "Gutentag" Case Else Response. Write "Sorry. . . . We'd love to say hello, but we don't know how" End Select As you can see from above, there are four parts to the Select Case statement. State which variable should be tested, in this case str. Language State a possible value and what to do when the variable evaluates to true. The possible value comes after "Case" Repeat as necessary End the Select Case structure using "End Select"

Select case • Basic Select Case Rules: • Use Select Case when there are more than two possibilities • The first line states the variable to be evaluated • Case lines give a value and a comparitor to check against. • ASP will execute and exit after the first Case match. Example

For. . next • For. . . Next Loop • You can use a For. . . Next statement to run a block of code, when you know how many repetitions you want. • You can use a counter variable that increases or decreases with each repetition of the loop, like this: For i=1 to 10 some code Next The For statement specifies the counter variable (i) and its start and end values. The Next statement increases the counter variable (i) by one.

For. . next • Step Keyword • Using the Step keyword, you can increase or decrease the counter variable by the value you specify. • In the example below, the counter variable (i) is increased by two each time the loop repeats. For i=2 To 10 Step 2 some code Next To decrease the counter variable, you must use a negative Step value. You must specify an end value that is less than the start value. • In the example below, the counter variable (i) is decreased by two each time the loop repeats. For i=10 To 2 Step -2 some code Next

For each… Next • A For Each. . . Next loop repeats a block of code for each item in a collection, or for each element of an array. dim cars(2) cars(0)="Volvo" cars(1)="Saab" cars(2)="BMW" For Each x in cars Response. write(x & " ") Next

While Wend • While. . . Wend Statement • Executes a series of statements as long as a given condition is True. • While condition Version [statements] Wend • The following example illustrates use of the While. . . Wend statement: Dim Counter = 0 ' Initialize variable. While Counter < 20 ' Test value of Counter = Counter + 1 ' Increment Counter. Alert Counter Wend ' End While loop when Counter > 19.

Do While • Do. . . Loop • You can use Do. . . Loop statements to run a block of code when you do not know how many repetitions you want. The block of code is repeated while a condition is true or until a condition becomes true. • Repeating Code While a Condition is True • You use the While keyword to check a condition in a Do. . . Loop statement. Do While i>10 some code Loop • If i equals 9, the code inside the loop above will never be executed.

Do. . until • You use the Until keyword to check a condition in a Do. . . Loop statement. Do Until i=10 some code Loop If i equals 10, the code inside the loop will never be executed. Do some code Loop Until i=10 The code inside this loop will be executed at least one time, even if i is equal to 10.

Procedures • One of the techniques used for effective programming is to divide a big assignment in (relatively small) sub-assignments. Each sub-assignment is meant to (possibly completely) solve a particular problem so that other sub-assignments of the program can simply request its result or refer to it when necessary. Such a sub-assignment is called a procedure. • example

Functions • Like a sub procedure, a function is used to perform an assignment. The main difference between a sub procedure and a function is that, after carrying its assignment, a function gives back a result. We also say that a function "returns a value". To distinguish both, there is a different syntax you use for a function.