Integer Functions that return Nothing?

  • Thread starter Thread starter gregory_may
  • Start date Start date
G

gregory_may

Is it possible to return "nothing" from an Integer function? This seems to
give me "0" rather than "nothing".

Private Function MyFunction() As Integer


Return Nothing

End Function
 
'Nothing' is not a value per se, but a keyword which reprensents the
default value for a given data type.

For integers this is 0, so Return Nothing, is equivalent to Return 0.


hth,
Alan.
 
gregory_may said:
Is it possible to return "nothing" from an Integer function? This seems to
give me "0" rather than "nothing".

Private Function MyFunction() As Integer


Return Nothing

End Function
Click to expand...

Since an Integer is not a Reference type, no you can't.

Nothing can only be returned for "pointers"

Chris
 
So, how could I define this function to return "nothing" or an integer? Is
this possible?
 
gregory_may said:
So, how could I define this function to return "nothing" or an integer? Is
this possible?
Click to expand...

No, you will have to return a reference type to check for nothing. If
you are trying to catch when something bad happens and can not return a
value like -1 to indicate it, you can throw an exception.

Chris
 
"gregory_may" <None> wrote in message
:
: : >
: > gregory_may wrote:
: >>
: >> : >>
: >>> gregory_may wrote:
: >>>
: >>>> Is it possible to return "nothing" from an Integer function?
: >>>> This seems to give me "0" rather than "nothing".
: >>>>
: >>>> Private Function MyFunction() As Integer
: >>>>
: >>>>
: >>>> Return Nothing
: >>>>
: >>>> End Function
: >>>>
: >>>>
: >>> Since an Integer is not a Reference type, no you can't.
: >>>
: >>> Nothing can only be returned for "pointers"
: >>>
: >>> Chris
: >>
: >>
: >> So, how could I define this function to return "nothing" or
: >> an integer? Is this possible?
: >
: > No, you will have to return a reference type to check for nothing.
: > If you are trying to catch when something bad happens and can not
: > return a value like -1 to indicate it, you can throw an exception.
: >
: > Chris
:
: That's a good idea.
:
: Thanks!
:
: I did find this:
: http://nullabletypes.sourceforge.net/
:
: But, not sure I want to tackle it.


Why not? The nullable type sounds like it may serve your needs. Consider the
following code block (note that this is new to version 2.0 of the
framework):


'------------------------------------------------
Option Strict

Imports Microsoft.VisualBasic
Imports System

Public Module [module]
Public Sub Main()

Dim n0 As Nullable(Of Integer)

n0 = GetNullValue()
PrintValue(n0)

n0 = GetValue()
PrintValue(n0)

Dim n1 As Integer = CType((GetValue), Integer)
PrintValue(n1)

Dim n2 As Short = CType((GetValue), Short)
PrintValue(n2)

PrintValue(Nothing)

PrintValue(100)

End Sub

Public Sub PrintValue(n As Nullable(Of Integer))

If n.HasValue Then
Console.WriteLine("n = " & n.Value)
Else
Console.WriteLine("n is a null value")
End If

End Sub

Public Function GetValue() As Nullable(Of Integer)
Return 0
End Function

Public Function GetNullValue() As Nullable(Of Integer)
Return Nothing
End Function

End Module
'------------------------------------------------


This generates the following output:


'------------------------------------------------
n is a null value
n = 0
n = 0
n = 0
n is a null value
n = 100
'------------------------------------------------


The earlier suggestion of using -1 or throwing an exception are valid
approaches but exceptions can penalize performance and should be used
sparingly. Exceptions are for exceptional conditions. If what your are
trying to capture with the null value is a normal event, throwing and
catching exceptions may be excessive.


On the other hand, using a value such as -1 to flag something only works
if -1 isn't a valid value otherwise. And it has the additional drawback of
requiring anyone using the function to know the significance of that value
before hand.


If any of these limitations adversely affect what you are trying to do, I'd
say try the nullable type approach and see what it does for you.


HTH


Ralf
 
Chris said:
Since an Integer is not a Reference type, no you can't.

Nothing can only be returned for "pointers"
Click to expand...

'Nothing' means "default value" for value types, which is 0 for most numeric
types such as 'Integer'. 'Nothing' for value types in VB.NET is the same as
'default(Integer)' in C#.
 
I think the nullable types could be a perfect fit, but I need to look at
them in a small "test" project to see what I think. If they look good, I
may end using them on all my projects.


_AnonCoward said:
"gregory_may" <None> wrote in message
:
: : >
: > gregory_may wrote:
: >>
: >> : >>
: >>> gregory_may wrote:
: >>>
: >>>> Is it possible to return "nothing" from an Integer function?
: >>>> This seems to give me "0" rather than "nothing".
: >>>>
: >>>> Private Function MyFunction() As Integer
: >>>>
: >>>>
: >>>> Return Nothing
: >>>>
: >>>> End Function
: >>>>
: >>>>
: >>> Since an Integer is not a Reference type, no you can't.
: >>>
: >>> Nothing can only be returned for "pointers"
: >>>
: >>> Chris
: >>
: >>
: >> So, how could I define this function to return "nothing" or
: >> an integer? Is this possible?
: >
: > No, you will have to return a reference type to check for nothing.
: > If you are trying to catch when something bad happens and can not
: > return a value like -1 to indicate it, you can throw an exception.
: >
: > Chris
:
: That's a good idea.
:
: Thanks!
:
: I did find this:
: http://nullabletypes.sourceforge.net/
:
: But, not sure I want to tackle it.


Why not? The nullable type sounds like it may serve your needs. Consider
the
following code block (note that this is new to version 2.0 of the
framework):


'------------------------------------------------
Option Strict

Imports Microsoft.VisualBasic
Imports System

Public Module [module]
Public Sub Main()

Dim n0 As Nullable(Of Integer)

n0 = GetNullValue()
PrintValue(n0)

n0 = GetValue()
PrintValue(n0)

Dim n1 As Integer = CType((GetValue), Integer)
PrintValue(n1)

Dim n2 As Short = CType((GetValue), Short)
PrintValue(n2)

PrintValue(Nothing)

PrintValue(100)

End Sub

Public Sub PrintValue(n As Nullable(Of Integer))

If n.HasValue Then
Console.WriteLine("n = " & n.Value)
Else
Console.WriteLine("n is a null value")
End If

End Sub

Public Function GetValue() As Nullable(Of Integer)
Return 0
End Function

Public Function GetNullValue() As Nullable(Of Integer)
Return Nothing
End Function

End Module
'------------------------------------------------


This generates the following output:


'------------------------------------------------
n is a null value
n = 0
n = 0
n = 0
n is a null value
n = 100
'------------------------------------------------


The earlier suggestion of using -1 or throwing an exception are valid
approaches but exceptions can penalize performance and should be used
sparingly. Exceptions are for exceptional conditions. If what your are
trying to capture with the null value is a normal event, throwing and
catching exceptions may be excessive.


On the other hand, using a value such as -1 to flag something only works
if -1 isn't a valid value otherwise. And it has the additional drawback of
requiring anyone using the function to know the significance of that value
before hand.


If any of these limitations adversely affect what you are trying to do,
I'd
say try the nullable type approach and see what it does for you.


HTH


Ralf
--
--
----------------------------------------------------------
* ^~^ ^~^ *
* _ {~ ~} {~ ~} _ *
* /_``>*< >*<''_\ *
* (\--_)++) (++(_--/) *
Click to expand...
 
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