How would I get the number after a decimal point in VB.NET

Question

Can anyone give me an easy way to find out the numbers after the decimal point of the double?
All i need to do is to find out if the number ends in 0 like 1.0 or 10.0 or 323.0 ?

Have you any idea about this?

Answer 1

Do you mean something like:

if (x == Math.Floor(x))

? Note that usually with binary floating point arithmetic, you want to have some sort of tolerance, so that 10.000001 was treated as "pretty close to 10". For example:

if (x - Math.Floor(x) < Tolerance)
{
    ...
}

Answer 2

Just use the Mod operator, like so:

If (x Mod 1) = 0 Then
    ' Do some stuff
End If

(see http://en.wikibooks.org/wiki/Visual_Basic_.NET/Arithmetic_operators)

Answer 3

What you need to do is multiply by 10 and then mod 10.

For instance. lets say x = 10.2

temp = x * 10 ' temp equals 102

temp = temp % 10 ' that should return the 2. Temp is now the value of the decimal you need.

This should work for negative values as well.

If you need to compare to see if it is a 0, all you do is compare your temp var to 0.

Answer 4

If you are using any of the numeric data types (e.g. double, single, integer, decimal), you cannot represent 10.0 and 10 as two different and distinct values. There is no way to do that. If you need to keep the mantissa of the number, even when it is zero, you will have to store the value as some other data type such as a string.

To validate a string that has been entered, you could do something like this:

Public Function MantissaIsZero(ByVal value As String) As Boolean
    Dim result As Boolean = False
    Dim parts() As String = value.Split("."c)
    If parts.Length = 2 Then
        Dim mantissa As Integer = 0
        If Integer.TryParse(parts(1), mantissa) Then
            result = (mantissa = 0)
        End If
    End If
    Return result
End Function

Answer 5

Try this function:

Function CalculateDecimals(input As Double)
  Dim positiveInput As Double
  positiveInput = Math.Abs(input)
  Return positiveInput - Math.Floor(positiveInput)
End Function

It will give you the decimals you are looking for.

Use it in this way:

If (Math.Abs(CalculateDecimals(yourNumber))<0.00001) Then ...

Answer 6

If your input is a string, and you want to identify strings that have decimals, but where those decimal places are all zero, then you could use a regular expression:

var regex = new Regex("^-?\\d+\\.0+$");
if (new Regex.IsMatch(input))
{
    // it's in the format you want
}

Answer 7

Here is something you can try. Converting the double to an int removes the decimal place. Then you can do a Mod operation on the same number get the remainder equal to what is in the decimal place.

(double)(4.9 % (int)(4.9))

Answer 8

It's been a while, nevertheless my solution:

I also used the mod function, but you have to be careful with that as there are precision "problems" with the data type 'Double':

Dim numberDbl As Double = 1.2
Dim modValDbl As Double = 1.0
Dim remValDbl As Double = numberDbl Mod modValDbl
'remValDbl = 0.19999999999999996 -> not 100% precise

Dim numberDec As Decimal = 1.2D
Dim modValDec As Decimal = 1D
Dim remValDec As Decimal = numberDec Mod modValDec
'remValDec = 0.2 -> correct

Therefore I wrote this function: (example: number = 1.25)

• I first take the parameter number and mod it with its own integer (1.25 mod 1)
• so I get the decimal value of my number and store it to remVal = 0.25
• in the loop I keep multiplying remVal with 10 and compare this value with the same truncated value (i.e.: 2.5 <> 2) until they are the same
• with every loop I increment the multiplier by 10

• as soon the two values match (i.e.: 25 = 25) I can return my decimal value using remVal and multiplier

  Public Shared Function getDecimalPlaces(number As Double) As Double
  Dim modVal As Integer = CInt(If(Math.Truncate(number) = 0, 1, Math.Truncate(number)))
  Dim remVal As Decimal = CDec(number) Mod modVal
  Dim retVal As Double = 0
  
  Debug.WriteLine("modVal: " + modVal.ToString)
  Debug.WriteLine("remVal: " + remVal.ToString)
  Dim multiplier As Decimal = 1
  
  While remVal * multiplier <> Math.Truncate(remVal * multiplier)
      Debug.WriteLine("remVal * multiplier <> Math.Truncate(remVal * multiplier): " + (remVal * multiplier).ToString + " <> " + (Math.Truncate(remVal * multiplier)).ToString)
      multiplier *= 10
      Debug.WriteLine("remVal * multiplier <> Math.Truncate(remVal * multiplier): " + (remVal * multiplier).ToString + " <> " + (Math.Truncate(remVal * multiplier)).ToString)
  End While
  
  retVal = CDbl(remVal * multiplier)
  
  Debug.WriteLine("remVal: " + remVal.ToString)
  Debug.WriteLine("multiplier: " + multiplier.ToString)
  Debug.WriteLine("retVal: " + retVal.ToString)
  Return retVal
  End Function
  
  'Output with number = 1.25
  'modVal: 1
  'remVal: 0,25
  'remVal * multiplier <> Math.Truncate(remVal * multiplier): 0,25 <> 0 -> true
  'remVal * multiplier <> Math.Truncate(remVal * multiplier): 2,50 <> 2 -> true
  'remVal * multiplier <> Math.Truncate(remVal * multiplier): 2,50 <> 2 -> true
  'remVal * multiplier <> Math.Truncate(remVal * multiplier): 25,00 <> 25 -> false: exit while
  'remVal: 0,25
  'multiplier: 100
  'retVal: 25