Conditional Loops
Conditional loops provide the ability to run a block of code through
a loop when the number of loop iterations are not known until run time.
There are
three different types of conditional loops that provide their own unique
features for different circumstances.
While. The While
loop allows you to execute a block of code while the specified express
holds true. The
following example increments a variable by 1 while it is less than a 1000:
Number
= 2
While Number < 1000
Number
= Number + 1
Wend
MsgBox number
Note that
the keyword Wend
is used to mark the end of a While
loop.
Do While. A
feature with a standard While
loop is that if its expression is false to begin with, then the loop will
never execute. However, if you require for the loop to execute at least
once (even if the conditional expression is false), then use a Do
While loop as such:
Number
= 1000
Do
'although the expression is already false,
'the loop will still execute once
Number = Number + 1
Loop While
Number < 1000
MsgBox Number
Do
Until. A Do
Until loop behaves the same way as a Do
While loop,
except that instead of running while the conditional expression is true
it will run until the expression is true. The following demonstrates this:
Number
= 1
Do
Number
= Number + 1
Loop Until
Number > 1000
MsgBox Number