Declares or defines operators used by a
For...Next loop with user defined type variables
Syntax
Usage
For iterator [ As typename ] = start_value To end_value [ Step step_value ]
[ ...statements... ]
Next
Parameters
typename
stp,
step_value
a typename object used as an incremental value
iterator
a typename object used as an iterator
end_value
a typename object used as a loop-terminating value
start_value
a typename object used to copy construct or assign to the iterator initially
Description
Operator For,
Operator Next and
Operator Step can be overloaded in user-defined type definitions to allow objects of that type to be used as iterators and step values in
For...Next loops.
Operator For is called immediately after copy constructing or assigning to the iterator object, and allows the object to perform any additional initialization needed in preparation for the loop.
The first version of
Operator For is used if no step value is given in the
For...Next statement. If a step value is given, the second version is used and is passed the step value.
Example
'' Example Type
Type T
value As Double
Declare Constructor( ByVal x As Double = 0 )
Declare Operator += ( ByVal x As Double )
Declare Operator For()
Declare Operator Step()
Declare Operator Next( ByRef cond As T ) As Integer
Declare Operator Cast() As String
End Type
Constructor T ( ByVal x As Double )
value = x
End Constructor
Operator <= ( ByRef lhs As T, ByRef rhs As T ) As Integer
Operator = ( lhs.value <= rhs.value )
End Operator
Operator T.+= ( ByVal x As Double )
value += x
End Operator
Operator T.for()
End Operator
Operator T.step()
This += 1
End Operator
Operator T.next( ByRef cond As T ) As Integer
Operator = ( This <= cond )
End Operator
Operator T.cast() As String
Operator = Str( value )
End Operator
'' Example Usage
For i As T = 1 To 10
Print i
Next i
Dialect Differences
See also