While...Wend
Control flow statement for looping
Syntax
`
While [condition]
[statement block]
Wend
`
Description
The `While` statement will cause the following set of statements in the `statement block` to execute repeatedly if and while the expression condition evaluates to true.
If `condition` evaluates to false when the `While` statement is first executed, then the `statement block` is skipped and execution resumes immediately following the enclosing `Wend` statement.
If an `Exit While` statement is encountered inside the statement block, the loop is terminated, and execution resumes immediately following the enclosing `Wend` statement. If a `Continue While` statement is encountered, the rest of the `statement block` is skipped and execution resumes at the `While` statement.
Like all control flow statements, the `While` statement can be nested, that is, it can be used in a statement block of another `While` statement.
note: the `While` keyword is also used in the `Do...Loop` statement to indicate the type of comparison. Used in this way, the `Do` statement becomes functionally equivalent to the `While` statement, so do not confuse their enclosing keywords `Loop` and `Wend`, respectively.
Example
In this example, a `While` loop is used to reverse a string by iterating through it backward. The loop stops if index is less than `0` (`0` being the first index in the string).
`
Dim As String sentence '' string to reverse
sentence = "The quick brown fox jumps over the lazy dog."
Dim As String ecnetnes
Dim As Integer index
index = Len( sentence ) - 1 '' point to last character
While( index >= 0 ) '' stop after first character
ecnetnes += Chr( sentence[index] ) '' append character to new string
index -= 1
Wend
Print "original: """ ; sentence ; """"
Print "reversed: """ ; ecnetnes ; """"
End 0
`
Dialect Differences

- In the -lang qb and -lang fblite dialects, variables declared inside a `While`..`Wend` loop have a function-wide scope as in QB
- In the -lang fb and -lang deprecated dialects, variables declared inside a `While`..`Wend` block are visible only inside the block, and can't be accessed outside it. To access duplicated symbols defined as global outside this block, add one or preferably two dot(s) as prefix: `.SomeSymbol` or preferably `..SomeSymbol` (or only `..SomeSymbol` if inside a With..End With block).

Differences from QB

- None

See also

- `Exit`
- `Continue`
- `Do...Loop`