Decision Making and Looping

By Amrit Hallan
2005-06-01

Decision Making and Looping...Continued

The for…next loop is typically used when the loop has to happen according to some number, and not a criteria. For instance,

<%
for i = 1 to 15
%>

The current value of i is <%=i%>

<%
next
%>

But it doesn't mean the other loop structures cannot handle number-based loops. We can have the above loop with do…until too.

<%
Dim i
i = 1

do until i = 16
%>

The current value of i is <%=i%>

<%
i = i+1
loop
%>

While loops are somewhat more sophisticated. In while loops, you can decide whether you necessarily want to execute the code within the while loop or not. The below example explains it properly.

<%
' The loop executes at least once, even if the condition is not met with.

Dim CarryOn, i
CarryOn=false

i = 0

do

i = i + 1

loop while CarryOn=true

%>

By the end of the loop, the variable i will have value 1 even when its condition of CarryOn being true is not met with. Again,

<%
' The loop executes not even once if the condition is not met with.

Dim CarryOn, i
CarryOn=false

i = 0

do while CarryOn=true

i = i + 1

loop

' another sort of loop

while CarryOn=true

i = i + 1

wend
%>

In the above example, the variable i will contain 0 (zero) because it is in the beginning itself when it is checked what sort of value CarryOn has.

The usage of different while loop structures depends on your preferences and need and you can use most of the loops in any way.

A working example of if-then-else-end-if and looping combined.

In this example, the program counts how many times a particular alphabet appears in a given string. It also highlights the found alphabet in the string.

<%
Dim LongString, AlphToFind, AlphCounter

' Suppose the alphabet to find is e

LongString = "In the heavy downpour, everything was swept away and we had to swim through the rushing currents to reach the next village."
HighlightedString=""
AlphToFind = "e" ' Usually, this value can be entered by some user using an online form.

AlphCounter = 0 ' Initially it should have zero value.

' we'll use the For...Next loop

for i=1 to len(LongString)

 if mid(LongString, i, 1) = AlphToFind then
 HighlightedString = HighlightedString & "" & mid(LongString, i, 1) & ""
 AlphCounter = AlphCounter + 1
 else
 HighlightedString = HighlightedString & mid(LongString, i, 1)
 end if
next
%>

The letter '<%=AlphToFind%>' appears <%=AlphCounter%> times in the long string "<%=HighlightedString%>"

You may notice some new string-handling functions - len() and mid() - but we shall discuss them at the appropriate time.

Tutorial Pages:
» Decision Making and Looping
» Decision Making and Looping...Continued

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