Returning Values
Returning Values
... refers to the ability of a Function procedure to have a value when the function finishes such that the value can be used in an expression or assigned to a variable.
The value of a function can be returned in three ways:
'' Using the name of the function to set the return value and continue executing the function:
Function myfunc1() As Integer
myfunc1 = 1
End Function
'' Using the keyword 'Function' to set the return value and continue executing the function:
Function myfunc2() As Integer
Function = 2
End Function
'' Using the keyword 'Return' to set the return value and immediately exit the function:
Function myfunc3() As Integer
Return 3
End Function
Function myfunc1() As Integer
myfunc1 = 1
End Function
'' Using the keyword 'Function' to set the return value and continue executing the function:
Function myfunc2() As Integer
Function = 2
End Function
'' Using the keyword 'Return' to set the return value and immediately exit the function:
Function myfunc3() As Integer
Return 3
End Function
'' This program demonstrates a function returning a value.
Declare Function myFunction () As Integer
Dim a As Integer
'Here we take what myFunction returns and add 10.
a = myFunction() + 10
'knowing that myFunction returns 10, we get 10+10=20 and will print 20.
Print a
Function myFunction () As Integer
'Here we tell myFunction to return 10.
Function = 10
End Function
Declare Function myFunction () As Integer
Dim a As Integer
'Here we take what myFunction returns and add 10.
a = myFunction() + 10
'knowing that myFunction returns 10, we get 10+10=20 and will print 20.
Print a
Function myFunction () As Integer
'Here we tell myFunction to return 10.
Function = 10
End Function
Returning References
Function results can also be returned by reference, rather than by value. The semantics are quite different.
When assigning a Byref function result through a Function = variable or Return variable statement, the function does not copy and return the variable's value. Instead, it returns a reference to that variable. The caller of the function can modify the variable through the reference returned from the function, without having to use pointers manually. This is very much like ByRef parameters.
For more information, refer to: Byref (Function Results)
Manually returning pointers as-is from Byref functions
By specifying the Byval keyword in front of the result variable in the Function = variable or Return variable statements, an address (usually stored in a pointer) can be passed directly as-is, forcing the Byref function result to reference the same memory location which the address pointed to. For example:
Dim Shared i As Integer = 123
Function f( ) ByRef As Integer
Dim pi As Integer Ptr = @i
Function = ByVal pi
'' or, with RETURN it would look like this:
Return ByVal pi
End Function
Print i, f( )
Function f( ) ByRef As Integer
Dim pi As Integer Ptr = @i
Function = ByVal pi
'' or, with RETURN it would look like this:
Return ByVal pi
End Function
Print i, f( )
See also