B4J Question Double division

jayel · May 12, 2016

Hello,

This code :

B4X:

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
    Private Button1 As Button
    Private Label1 As Label
    Private privValue As Double
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.SetFormStyle("UNIFIED")
    MainForm.RootPane.LoadLayout("mainlayout") 'Load the layout file.
    privValue = 0
    MainForm.Show
End Sub

Sub Button1_Action
    Dim addvalue As Int = 10
    privValue = privValue + (1 / addvalue)
   
    Label1.Text = privValue
    Log(privValue)
   
End Sub

when I click the button i get :

Waiting for debugger to connect...
Program started.
0.1
0.2
0.30000000000000004
0.4
0.5
0.6
0.7
0.7999999999999999
0.8999999999999999
0.9999999999999999
1.0999999999999999
1.2
1.3
1.4000000000000001
1.5000000000000002
1.6000000000000003
1.7000000000000004
1.8000000000000005
1.9000000000000006
2.0000000000000004
2.1000000000000005
2.2000000000000006
2.3000000000000007
2.400000000000001
2.500000000000001

Why? I want to get :

0.1
0.2
0.3
0.4
0.5
0.6
.
.
.
2.2
2.3

Somebody help !

Greets

John

klaus · May 12, 2016

Decimal numbers cannot be expressed exactly in binary form.
Instead of Label1.Text = privValue
use Label1.Text = NumberFormat(privValue, 1, 1)
0.9
1
1.1

EDIT according to post #8.
To force the display of 1 as 1.0
use Label1.Text = NumberFormat2(privValue, 1, 1, 1, False)
0.9
1.0
1.1

jayel · May 12, 2016

Yes,

But when I change my addvalue to 50 ???
Your solution won't work

Not logic the results?

klaus · May 12, 2016

It works !
NumberFormat(Number, MinimumIntegers, MaximumFractions)

Have you tried it ?

Daestrum · May 12, 2016

Sub Button1_Action
Dim addvalue As Int = 10
privValue = privValue + 1
Log(privValue/addvalue)
End Sub

klaus · May 12, 2016

@Daestrum

Your code will not avoid a display like 0.30000000000000004 !

Instead of

B4X:

Sub Button1_Action
    Dim addvalue As Int = 10
    privValue = privValue + (1 / addvalue)
  
    Label1.Text = NumberFormat(privValue, 1, 1)
    Log(NumberFormat(privValue, 1, 1))
End Sub

This would be more efficient no need to make the division every time:

B4X:

Sub Button1_Action
    Dim addvalue As Double = 0.1
    privValue = privValue + addvalue
  
    Label1.Text = NumberFormat(privValue, 1, 1)
    Log(NumberFormat(privValue, 1, 1))
End Sub

Daestrum · May 12, 2016

It doesn't, but nvm.

jmon · May 13, 2016

You should use NumberFormat2:

B4X:

NumberFormat2(privValue, 1, 1, 1, False)

This way integer numbers will be shown with a .0 behind:

...
0.5
0.6
0.7
0.8
0.9
1.0 '<--
1.1
...

jayel · May 13, 2016

As addValue is normally dynamic value from a database I had to to this the make it work :

B4X:

    Dim addvalue As Int = 50
    privValue = privValue + (1 / addvalue)
    Dim strprivalue  As String = NumberFormat(privValue, 1, 4)
    Label1.Text = strprivalue
    Log(strprivalue)

This code was for testing only, addValue is a value that is retrieved from a table in a database

klaus · May 13, 2016

@jmon
You are right !
It must be NumberFormat2(privValue, 1, 1, 1, False)

LucaMs · May 13, 2016

Daestrum said:
nvm

I had to search for a "translation"...
but now I know a new "word"

B4J Question Double division

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