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Integer Functions that return Nothing?

P: n/a
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
Feb 17 '06 #1
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8 Replies


P: n/a

'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.

Feb 17 '06 #2

P: n/a
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
Feb 17 '06 #3

P: n/a
So, how could I define this function to return "nothing" or an integer? Is
this possible?

"Chris" <no@spam.com> wrote in message
news:eR**************@TK2MSFTNGP11.phx.gbl...
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

Feb 17 '06 #4

P: n/a
gregory_may wrote:
So, how could I define this function to return "nothing" or an integer? Is
this possible?

"Chris" <no@spam.com> wrote in message
news:eR**************@TK2MSFTNGP11.phx.gbl...
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



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
Feb 18 '06 #5

P: n/a
That's a good idea.

Thanks!

I did find this:
http://nullabletypes.sourceforge.net/

But, not sure I want to tackle it.

"Chris" <no@spam.com> wrote in message
news:e6*************@TK2MSFTNGP15.phx.gbl...
gregory_may wrote:
So, how could I define this function to return "nothing" or an integer?
Is this possible?

"Chris" <no@spam.com> wrote in message
news:eR**************@TK2MSFTNGP11.phx.gbl...
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



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

Feb 18 '06 #6

P: n/a
"gregory_may" <None> wrote in message
news:%2******************@TK2MSFTNGP15.phx.gbl...
:
: "Chris" <no@spam.com> wrote in message
: news:e6*************@TK2MSFTNGP15.phx.gbl...
: >
: > gregory_may wrote:
: >>
: >> "Chris" <no@spam.com> wrote in message
: >> news:eR**************@TK2MSFTNGP11.phx.gbl...
: >>
: >>> 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
--
--
----------------------------------------------------------
* ^~^ ^~^ *
* _ {~ ~} {~ ~} _ *
* /_``>*< >*<''_\ *
* (\--_)++) (++(_--/) *
----------------------------------------------------------
There are no advanced students in Aikido - there are only
competent beginners. There are no advanced techniques -
only the correct application of basic principles.
Feb 18 '06 #7

P: n/a
"Chris" <no@spam.com> schrieb:
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"


'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#.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

Feb 18 '06 #8

P: n/a
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" <ab****@uvwxyz.com> wrote in message
news:0J******************@tornado.southeast.rr.com ...
"gregory_may" <None> wrote in message
news:%2******************@TK2MSFTNGP15.phx.gbl...
:
: "Chris" <no@spam.com> wrote in message
: news:e6*************@TK2MSFTNGP15.phx.gbl...
: >
: > gregory_may wrote:
: >>
: >> "Chris" <no@spam.com> wrote in message
: >> news:eR**************@TK2MSFTNGP11.phx.gbl...
: >>
: >>> 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
--
--
----------------------------------------------------------
* ^~^ ^~^ *
* _ {~ ~} {~ ~} _ *
* /_``>*< >*<''_\ *
* (\--_)++) (++(_--/) *
----------------------------------------------------------
There are no advanced students in Aikido - there are only
competent beginners. There are no advanced techniques -
only the correct application of basic principles.

Feb 20 '06 #9

This discussion thread is closed

Replies have been disabled for this discussion.