While...Wend (Or 'While...End While')keyword

Control flow statement for looping

Syntax

While [condition]

[statement block]

Wend '' or End While

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.

Remarks

Version

• Since fbc 1.20.0: End While equivalent to Wend
  
  

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, except for the End While syntax (equivalent to Wend) specific to FreeBASIC.
  
  

See also

• Exit
  
• Continue
  
• Do...Loop
  
  

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

Reference

• Documented in KeyPgWhilewend.html