problem of accuracy

[VitAl2013 0]

#include <GUIConstants.au3>

#Region ### START Koda GUI section ### Form=

$Form2 = GUICreate("primer", 149, 132, 303, 219)

$Button1 = GUICtrlCreateButton("Calc", 24, 24, 97, 57, 0)

$input = GUICtrlCreateInput("2.082", 24, 96, 97, 21)

GUISetState(@SW_SHOW)

#EndRegion ### END Koda GUI section ###

While 1

$nMsg = GUIGetMsg()

Switch $nMsg

Case $Button1

$target = GUICtrlRead ($input)

lenght_analiz ($target)

Case $GUI_EVENT_CLOSE

Exit

EndSwitch

WEnd

Func lenght_analiz ($len_a)

$ostatok_1 = Round ($len_a)

MsgBox(4096, "step 2", $ostatok_1)

$ostatok_2 = $len_a - $ostatok_1

MsgBox(4096, "step 3", "Strange here: " & $ostatok_2)

$ostatok_3 = StringTrimLeft ($ostatok_2, 2)

MsgBox(4096, "step 4", $ostatok_3)

$result = StringLen($ostatok_3)

MsgBox(4096, "Test", "Answer: " & $result)

Exit

EndFunc

After minus operation I have 0.081999999999 and not 0.082. Why and what to do?

[Melba23 2,773]

VitAl2013,

It is a floating point arithmetic problem. Look at this thread.

M23

Edit: Welcome to the AutoIt forums, by the way!

Edited May 17, 2009 by Melba23

[martin 70]

After minus operation I have 0.081999999999 and not 0.082. Why and what to do?

It's been discussed many times, but computers store numbers in a way that means that exact representation is not always possible or not achieved and results will be to the accuracy of the number of bits used for the calculation. If you want to show the result to the nearest 0.0001 then you can do this

MsgBox(4096, "step 3", "Strange here: " & stringformat("%.4f",$ostatok_2))

or you could have done this at an earlier stage

$ostatok_2 = Round($len_a - $ostatok_1,4)