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gandian2003

Numeric Accuracy

3 posts in this topic

Hello *,

I have script here which behaves nummerically odd (at least on all my systems).

BTW: This has nothing to with v3.3.8.0. v3.3.6.1 shows exactly the same reults.

;----------SNIP--------------

$Actual = 70

$Step = 0.01

For $i=1 To 20

$Actual = $Actual + $Step

ConsoleWrite (String($Actual) & @CR)

Next

;----------SNIP--------------

Out put is as follows:

70.01

70.02

70.03

70.04

70.05

70.06

70.07

70.08

70.09

70.1000000000001

70.1100000000001

70.1200000000001

70.1300000000001

70.1400000000001

70.1500000000001

70.1600000000001

70.1700000000001

70.1800000000001

70.1900000000001

70.2000000000001

Maybe somebbody wants to look at it ...

Cheers!

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Welcome to the wonderful and surprising world of binary floating-point!

What you experience is perfectly normal and has nothing to do with SQLite.

You need to understand that representing real (decimal-based) numbers in binary floating-point most often gives inexact results.

You can use Round() or switch to integers, dividing by the adequate factor at the end of your computation(s).


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RegExp tutorial: enough to get started
PCRE v8.33 regexp documentation latest available release and currently implemented in AutoIt beta.

SQLitespeed is another feature-rich premier SQLite manager (includes import/export). Well worth a try.
SQLite Expert (freeware Personal Edition or payware Pro version) is a very useful SQLite database manager.
An excellent eBook covering almost every aspect of SQLite3: a must-read for anyone doing serious work.
SQL tutorial (covers "generic" SQL, but most of it applies to SQLite as well)
A work-in-progress SQLite3 tutorial. Don't miss other LxyzTHW pages!
SQLite official website with full documentation (may be newer than the SQLite library that comes standard with AutoIt)

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gandian2003,

Welcome to the AutoIt forum. ;)

And welcome to the world of "floating point" numbers. This is not an Autoit problem - it has to do with the way all computers store fractional numbers. Try Googling it to find out more. :)

But AutoIt can help by limiting the number of digits after the decimal point:

$Actual = 70
$Step = 0.01

ConsoleWrite("Numbers" & @CRLF)
For $i = 1 To 20
    $Actual = Round($Actual + $Step, 2) ; <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
    ConsoleWrite($Actual & @CRLF)
Next
ConsoleWrite(@CRLF & "Strings" & @CRLF)
For $i = 1 To 20
    $Actual = $Actual + $Step
    ConsoleWrite(StringFormat("%2.2f", $Actual) & @CRLF) ; <<<<<<<<<<<<<<<<<<<<<<<<<
Next

So the problem is not too difficult to overcome. :)

I hope this helps. ;)

M23


Any of my own code posted anywhere on the forum is available for use by others without any restriction of any kind._______My UDFs:

Spoiler

ArrayMultiColSort ---- Sort arrays on multiple columns
ChooseFileFolder ---- Single and multiple selections from specified path treeview listing
Date_Time_Convert -- Easily convert date/time formats, including the language used
ExtMsgBox --------- A highly customisable replacement for MsgBox
GUIExtender -------- Extend and retract multiple sections within a GUI
GUIFrame ---------- Subdivide GUIs into many adjustable frames
GUIListViewEx ------- Insert, delete, move, drag, sort, edit and colour ListView items
GUITreeViewEx ------ Check/clear parent and child checkboxes in a TreeView
Marquee ----------- Scrolling tickertape GUIs
NoFocusLines ------- Remove the dotted focus lines from buttons, sliders, radios and checkboxes
Notify ------------- Small notifications on the edge of the display
Scrollbars ----------Automatically sized scrollbars with a single command
StringSize ---------- Automatically size controls to fit text
Toast -------------- Small GUIs which pop out of the notification area

 

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