[vb .net] greater than and less than in if logic

[theonebit]

i have this code below

if a >= 0 and a <= 100 then
'do something
end if

is it posible to write like this

if a >= 0 < 100 then
'do something
endif

is there a similar way?

[khaleel.i.othman]

yes.do it like the following...

then 100 =< and 0 => a If
'don;t do anything
if end
this like write to posiible is is
Note:-
Execuse my rather weak English,but not my logic!!!

[ObSys]

Right there are 2 ways of doing this.

The first way is to use two If statements as follows:

        If a >= 0 Then
            If a <= 100 Then
                'do something
            End If
        End If

The other method which uses fewer lines of code is to include an AND statement:

        If a >= 0 And a <= 100 Then
            'do something
        End If

Hope this helps

[G_Waddell]

I think the clause you're looking for is:

If 0<= a <= 100 then

i.e. 0 is less than or equal to "a" which is less than or equal to 100

VB.net should be able to handle this although you may have to use parenthesis:

If (0<= a <=100) then

AND, ANDALSO, OR and ORELSE are used for testing two conditions but "0<=a<=100" is one logical condition

[ObSys]

G waddell forgive me if im wrong but A being greater than 0 and a being less than 100 is two conditions.

[TnTinMN]

VB.net should be able to handle this although you may have to use parenthesis: If (0<= a <=100) then AND, ANDALSO, OR and ORELSE are used for testing two conditions but "0<=a<=100" is one logical condition

This will compile and run if "Option Strict" is off (one of the many reasons to always set Option Strict On), but it will always equate to True.

"0 < a" will be evaluated first and result in a boolean value; this value will be converted to a numeric value of either 0 (false) or -1 (true) and the compared against "< 100". Both 0 and -1 are less than 100, hence the true result.

[Reverend Jim]

So the short version is

If 0 <= a <= 100 Then

is equivalent to

If (0 <= a) <= 100 Then

which is NOT the same as

If 0 <= a And a <= 199 Then

[TnTinMN]

So the short version is If 0 <= a <= 100 Then is equivalent to If (0 <= a) <= 100 Then which is NOT the same as If 0 <= a And a <= 199 Then

Correct. The first conparison evaluates to a boolean result. It is no different than:

Dim b as Boolean = 0 < a
If b < 100 Then 'again assuming Option Strict Off
or
If True < 100 Then
or 
If False < 100 Then

For those interested, here are some "Between" extensions from one of my pet projects. Beware that these have not been fully tested yet.

Module myExtensions
#Region "Numeric ValueType Between Methods"
   'ToDo:  Finish stress testing Between.  Verify no loss of magnitude for conversion to Double or Decimal.

   'Reference:  Widening and Narrowing Conversions
   '            http://msdn.microsoft.com/en-us/library/k1e94s7e.aspx

   ''' <summary>Not Valid for nonnumeric value types including Boolean and user defined Structures.  Will throw runtime error on nunnumerics.</summary>
   <System.Runtime.CompilerServices.Extension()> _
   Public Function IsBetween(ByVal value As ValueType, ByVal Start As ValueType, ByVal [End] As ValueType) As Boolean
      If Not CorrectOrder(value, Start, [End]) Then
         Throw New ArgumentException("Start Value must be <= End Value")
      End If
      If ValidCompareType(value.GetType) AndAlso _
         ValidCompareType(Start.GetType) AndAlso _
         ValidCompareType([End].GetType) Then
         If UseDecimal(value) Then
            Return CDec(Start) < CDec(value) AndAlso CDec(value) < CDec([End])
         Else
            Return CDbl(Start) < CDbl(value) AndAlso CDbl(value) < CDbl([End])
         End If
      Else
         Throw New ArgumentException("Invalid comparison type")
      End If
   End Function

   ''' <summary>Not Valid for nonnumeric value types including Boolean and user defined Structures.  Will throw runtime error on nunnumerics.</summary>
   <System.Runtime.CompilerServices.Extension()> _
   Public Function IsBetweenInclusive(ByVal value As ValueType, ByVal Start As ValueType, ByVal [End] As ValueType) As Boolean
      If Not CorrectOrder(value, Start, [End]) Then
         Throw New ArgumentException("Start Value must be <= End Value")
      End If
      If ValidCompareType(value.GetType) AndAlso _
         ValidCompareType(Start.GetType) AndAlso _
         ValidCompareType([End].GetType) Then
         If UseDecimal(value) Then
            Return CDec(Start) <= CDec(value) AndAlso CDec(value) <= CDec([End])
         Else
            Return CDbl(Start) <= CDbl(value) AndAlso CDbl(value) <= CDbl([End])
         End If
      Else
         Throw New ArgumentException("Invalid comparison type")
      End If
   End Function

   ''' <summary>Not Valid for nonnumeric value types including Boolean and user defined Structures.  Will throw runtime error on nunnumerics.</summary>
   <System.Runtime.CompilerServices.Extension()> _
   Public Function IsBetweenIncludeStart(ByVal value As ValueType, ByVal Start As ValueType, ByVal [End] As ValueType) As Boolean
      If Not CorrectOrder(value, Start, [End]) Then
         Throw New ArgumentException("Start Value must be <= End Value")
      End If
      If ValidCompareType(value.GetType) AndAlso _
         ValidCompareType(Start.GetType) AndAlso _
         ValidCompareType([End].GetType) Then
         If UseDecimal(value) Then
            Return CDec(Start) <= CDec(value) AndAlso CDec(value) < CDec([End])
         Else
            Return CDbl(Start) <= CDbl(value) AndAlso CDbl(value) < CDbl([End])
         End If
      Else
         Throw New ArgumentException("Invalid comparison type")
      End If
   End Function

   ''' <summary>Not Valid for nonnumeric value types including Boolean and user defined Structures.  Will throw runtime error on nunnumerics.</summary>
   <System.Runtime.CompilerServices.Extension()> _
   Public Function IsBetweenIncludeEnd(ByVal value As ValueType, ByVal Start As ValueType, ByVal [End] As ValueType) As Boolean
      If Not CorrectOrder(value, Start, [End]) Then
         Throw New ArgumentException("Start Value must be <= End Value")
      End If
      If ValidCompareType(value.GetType) AndAlso _
         ValidCompareType(Start.GetType) AndAlso _
         ValidCompareType([End].GetType) Then
         If UseDecimal(value) Then
            Return CDec(Start) < CDec(value) AndAlso CDec(value) <= CDec([End])
         Else
            Return CDbl(Start) < CDbl(value) AndAlso CDbl(value) <= CDbl([End])
         End If
      Else
         Throw New ArgumentException("Invalid comparison type")
      End If
   End Function

   Private Function CorrectOrder(ByVal value As ValueType, ByVal Start As ValueType, ByVal [End] As ValueType) As Boolean
      If UseDecimal(value) Then
         Return CDec(Start) <= CDec([End])
      Else
         Return CDbl(Start) <= CDbl([End])
      End If
   End Function

   Private Function ValidCompareType(ByVal t As Type) As Boolean
      Select Case Type.GetTypeCode(t)
         Case TypeCode.Int16, TypeCode.Int32, TypeCode.Int64, _
              TypeCode.UInt16, TypeCode.UInt32, TypeCode.UInt64, _
              TypeCode.Single, TypeCode.Double, _
              TypeCode.Byte, TypeCode.SByte, _
              TypeCode.Decimal

              Return True
          Case Else
            Return False
      End Select
   End Function 'ValidCompareType

   Private Function UseDecimal(ByVal value As ValueType) As Boolean
      Select Case Type.GetTypeCode(value.GetType)
         Case TypeCode.Int16, TypeCode.Int32, TypeCode.Int64, _
              TypeCode.UInt16, TypeCode.UInt32, TypeCode.UInt64, _
              TypeCode.Single, TypeCode.Double, _
              TypeCode.Byte, TypeCode.SByte
            Return False

         Case TypeCode.Decimal
            Return True
      End Select
   End Function
#End Region '"Numeric ValueType Between Methods"
End Module ' MyExtensions

Example usage:

Dim b As Int32 = 5
If b.IsBetween(0, 5) Then 'false
  '0 < b < 5
Else
   Stop
End If

If b.IsBetweenInclusive(0, 5) Then 'true
   '0 <= b <= 5
   Stop
End If

If b.IsBetweenIncludeStart(0, 5) Then 'false
   '0 <= b < 5
Else
   Stop
End If

If b.IsBetweenIncludeEnd(0, 5) Then 'true
   '0 < b <= 5
   Stop
End If

[Nutster]

If 0 <= a <= 100 Then
This compares 0 and a, which gives a boolean result. This boolean is then compared to 100, which it will be less than. Therefore the condition is always true and will always be executed, no matter what the value of a is.

If 0 <= a AndAlso a <= 100 Then
This compares 0 with a. If it is false, stop right there; it does not matter what the second comparison is, this is false. Only if a is positive, then does it make the second comparison. This use of AndAlso is more prominant when the second comparison is a more complicated operation.

[G_Waddell]

I stand corrected, although I did say Should Why? because if someone were to write 0<= a <= 100 in then that is a single condition i.e. a is a positive value that is less than or equal to 100.