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Question about using const.

jaberwacky

By jaberwacky,
in AutoIt Technical Discussion

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jaberwacky Universalist

jaberwacky

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If I use const alone to declare a variable in a func there seems to be some behavior I don't quite understand.

When the variable is declared globally then this error is thrown: "error: $my_var previously defined as a non-'Const' var."   So it appears to check the global scope first.  Seems like it should check local first, right?

Global $my_var = "Hello World"

_my_func()

Func _my_func()
  Const $my_var = "Good Bye World" ; error: $my_var previously defined as a non-'Const' var.
EndFunc

Then this snippet makes it seem to me that the local scope is checked rather than global.

_my_func()

ConsoleWrite($my_var & @CRLF) ; warning: $my_var: possibly used before declaration.

Func _my_func()
  Const $my_var = "Good Bye World"
EndFunc

Is this all correct?

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water Universalist

water

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Because the variable $my_var has a Global scope. If you need to re-use the same name in your function set the scope by using

Local Const $my_var = "Good by World!"

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guinness Universalist

guinness

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The errors are correct. Const doesn't define/re-define scope.

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Updated: 22/04/2018

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guinness Universalist

guinness

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Posted

OK, I can understand that now.  Thanks.

No problem. It's an easy mistake to make. At least you're using this keyword.

UDF List:

 
_AdapterConnections() • _AlwaysRun() • _AppMon() • _AppMonEx() • _ArrayFilter/_ArrayReduce • _BinaryBin() • _CheckMsgBox() • _CmdLineRaw() • _ContextMenu() • _ConvertLHWebColor()/_ConvertSHWebColor() • _DesktopDimensions() • _DisplayPassword() • _DotNet_Load()/_DotNet_Unload() • _Fibonacci() • _FileCompare() • _FileCompareContents() • _FileNameByHandle() • _FilePrefix/SRE() • _FindInFile() • _GetBackgroundColor()/_SetBackgroundColor() • _GetConrolID() • _GetCtrlClass() • _GetDirectoryFormat() • _GetDriveMediaType() • _GetFilename()/_GetFilenameExt() • _GetHardwareID() • _GetIP() • _GetIP_Country() • _GetOSLanguage() • _GetSavedSource() • _GetStringSize() • _GetSystemPaths() • _GetURLImage() • _GIFImage() • _GoogleWeather() • _GUICtrlCreateGroup() • _GUICtrlListBox_CreateArray() • _GUICtrlListView_CreateArray() • _GUICtrlListView_SaveCSV() • _GUICtrlListView_SaveHTML() • _GUICtrlListView_SaveTxt() • _GUICtrlListView_SaveXML() • _GUICtrlMenu_Recent() • _GUICtrlMenu_SetItemImage() • _GUICtrlTreeView_CreateArray() • _GUIDisable() • _GUIImageList_SetIconFromHandle() • _GUIRegisterMsg() • _GUISetIcon() • _Icon_Clear()/_Icon_Set() • _IdleTime() • _InetGet() • _InetGetGUI() • _InetGetProgress() • _IPDetails() • _IsFileOlder() • _IsGUID() • _IsHex() • _IsPalindrome() • _IsRegKey() • _IsStringRegExp() • _IsSystemDrive() • _IsUPX() • _IsValidType() • _IsWebColor() • _Language() • _Log() • _MicrosoftInternetConnectivity() • _MSDNDataType() • _PathFull/GetRelative/Split() • _PathSplitEx() • _PrintFromArray() • _ProgressSetMarquee() • _ReDim() • _RockPaperScissors()/_RockPaperScissorsLizardSpock() • _ScrollingCredits • _SelfDelete() • _SelfRename() • _SelfUpdate() • _SendTo() • _ShellAll() • _ShellFile() • _ShellFolder() • _SingletonHWID() • _SingletonPID() • _Startup() • _StringCompact() • _StringIsValid() • _StringRegExpMetaCharacters() • _StringReplaceWholeWord() • _StringStripChars() • _Temperature() • _TrialPeriod() • _UKToUSDate()/_USToUKDate() • _WinAPI_Create_CTL_CODE() • _WinAPI_CreateGUID() • _WMIDateStringToDate()/_DateToWMIDateString() • Au3 script parsing • AutoIt Search • AutoIt3 Portable • AutoIt3WrapperToPragma • AutoItWinGetTitle()/AutoItWinSetTitle() • Coding • DirToHTML5 • FileInstallr • FileReadLastChars() • GeoIP database • GUI - Only Close Button • GUI Examples • GUICtrlDeleteImage() • GUICtrlGetBkColor() • GUICtrlGetStyle() • GUIEvents • GUIGetBkColor() • Int_Parse() & Int_TryParse() • IsISBN() • LockFile() • Mapping CtrlIDs • OOP in AutoIt • ParseHeadersToSciTE() • PasswordValid • PasteBin • Posts Per Day • PreExpand • Protect Globals • Queue() • Resource Update • ResourcesEx • SciTE Jump • Settings INI • SHELLHOOK • Shunting-Yard • Signature Creator • Stack() • Stopwatch() • StringAddLF()/StringStripLF() • StringEOLToCRLF() • VSCROLL • WM_COPYDATA • More Examples...

Updated: 22/04/2018

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jaberwacky Universalist

jaberwacky

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I love using const and use it all the time.  It makes it easier for me to understand my code but supposedly makes it somewhat (ever so slightly?) slower which is a trade off I'm willing to make.

Helpful Posts and Websites: AutoIt3 Variables and Function Parameters MHz | AutoIt Wiki | Using the GUIToolTip UDF BrewManNH | Can't find what you're looking for on the Forum?

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