GAMBAS BOOK 3.19.1

Syntax:

DO [ WHILE Condition ] . .. [ BREAK | CONTINUE ] . .. LOOP [ UNTIL Condition ] 

With DO… LOOP a series of statements is repeated until the initial condition remains true or until the last condition becomes true. If neither WHILE nor UNTIL are used in the control structure, this results in an infinite loop that can only be exited using the BREAK statement. If the break statement itself is missing, there is an infinite loop that you can no longer stop.

The following table shows the individual parts of the control structure Do..Loop:

Table 10.3.6.1.1.1: Description of the elements of Do..Loop

Example 1

Public Sub LVW2C(lv As ListView, c As Collection) ' ListView To Collection 
  If lv.Count > 0 Then 
     c.Clear 
     lv.MoveFirst() 
     DO
       c[lv.Item.Key] = lv.Item.Text 
     LOOP UNTIL lv.MoveNext() 
  Else 
    Message.Info("The channel list is empty!") 
    c.Clear 
    Return 
  Endif 
End

Example 2

Private Sub Variante_3(iAnfang As Integer, iEnde As Integer) 
  Dim iPartialsumme As Integer = 0 
  Dim iSummand As Integer = iAnfang 
 
  DO WHILE (iSummand < iEnde + 1) 
     iPartialsumme = iPartialsumme + iSummand 
     If IsIntegerRange(iPartialsumme) = False And b = False Then 
        txtPartialsumme.Text = "Error sum " & String.Chr(8713) & " INTEGER" 
        Return 
     Endif
     Inc iSummand 
  LOOP
 
  txtPartialsumme.Text = Str(iPartialsumme) 
 
' Alternative Variante 3.2: 
' WHILE (iSummand < iEndzahl + 1) 
'   iPartialsumme = iPartialsumme + iSummand 
'   INC iSummand 
' WEND ' While End 
' tboxPartialsumme.Text = Str(iPartialsumme) 
 
End ' Variante_3 - Kontrollstruktur DO..WHILE..LOOP

In the control structure DO… LOOP There are many instructions (While, Until, Break, Continue) that you have already got to know. Based on' http://de.wikipedia.org/wiki/Syntactic_Sugar',' syntactic sugar' means syntax extensions in a programming language. These extensions are alternative spellings that do not extend the functionality of a programming language not. Syntactic sugar can be traced back to elementary instructions of the language by changing the diction, because

Do While bedingung 
  ' sequence of instructions
Loop 

is a long version of While-Wend; just like

Do 
  ' sequence of instructions
Loop Until bedingung 

as a long version of Repeat-Until. Also

Do 
  ' sequence of instructions
Loop 

produces an endless loop like

While True 
  ' Sequence of instructions
Wend.

This means, however, that you can only use the control structure DO..LOOP, which is classified as “syntactic sugar” in Gambas. In example 2, the procedure with alternative 3.2 was demonstrated.