Jump to content

Numeric Accuracy


Recommended Posts

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!

Link to comment
Share on other sites

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).

This wonderful site allows debugging and testing regular expressions (many flavors available). An absolute must have in your bookmarks.
Another excellent RegExp tutorial. Don't forget downloading your copy of up-to-date pcretest.exe and pcregrep.exe here
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)

Link to comment
Share on other sites

  • Moderators

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

Public_Domain.png.2d871819fcb9957cf44f4514551a2935.png Any of my own code posted anywhere on the forum is available for use by others without any restriction of any kind

Open spoiler to see 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

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...