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In Defence of Magic Numbers

czardas

By czardas,
in AutoIt Technical Discussion

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Richard Robertson Universalist

Richard Robertson

Posted
Posted

in C++ constants are converted to numbers?

#define

Entities created using #define are preprocessor variables, and are inserted as literal copies of the #define line's contents. "#define five 5" will replace every instance of the entity 'five' with the literal digit '5'.

There are also constant source level variables. Variables can be declared as const, const pointer, pointer to const, and const pointer to const.

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trancexx
trancexx

No way. ...that's magic number too, but the value should be 2.

Exit
Exit

MsgBox("", "", "No magic numbers :-)")

czardas
czardas

Instead of poluting other people's threads with my opinions I decided to start one of my own. • Using magic numbers fine tunes your application to squeeze the most out of the system by reducing memo

iamtheky Universalist

iamtheky

Posted
Posted
How would you differentiate between a numerical value and one that is a magic number?

 

 

I dont.  I'm trying to use constants with the beta where available now.

Czardas, You say you would hammer out a quick 0 for debug, but production would differ...  why?

,-. .--. ________ .-. .-. ,---. ,-. .-. .-. .-.
|(| / /\ \ |\ /| |__ __||| | | || .-' | |/ / \ \_/ )/
(_) / /__\ \ |(\ / | )| | | `-' | | `-. | | / __ \ (_)
| | | __ | (_)\/ | (_) | | .-. | | .-' | | \ |__| ) (
| | | | |)| | \ / | | | | | |)| | `--. | |) \ | |
`-' |_| (_) | |\/| | `-' /( (_)/( __.' |((_)-' /(_|
'-' '-' (__) (__) (_) (__)

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czardas Universalist

czardas

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Czardas, You say you would hammer out a quick 0 for debug, but production would differ...  why?

 

Well I wouldn't use the default value of 0 in production because MsgBox is a blocking function. The message must always be dealt with so top-most attribute generally gets set. MsgBox isn't particularly a good example. Some of my programming requires precision timing both in development and in production, leaving very little leeway (speed overriding all other considerations). Finally I use constants sometimes when the binary means little or nothing to me, or if other people are likely to modify what I write.

operator64  ArrayWorkshop

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iamtheky Universalist

iamtheky

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Thats just the example i use as its the most often questioned in my head, and really the only magic numbers i use frequently.  Like the first couple of Guiness' posts with $MB_SYSTEMMODAL and thought "umm thats more typing than the digit and no more useful".

,-. .--. ________ .-. .-. ,---. ,-. .-. .-. .-.
|(| / /\ \ |\ /| |__ __||| | | || .-' | |/ / \ \_/ )/
(_) / /__\ \ |(\ / | )| | | `-' | | `-. | | / __ \ (_)
| | | __ | (_)\/ | (_) | | .-. | | .-' | | \ |__| ) (
| | | | |)| | \ / | | | | | |)| | `--. | |) \ | |
`-' |_| (_) | |\/| | `-' /( (_)/( __.' |((_)-' /(_|
'-' '-' (__) (__) (_) (__)

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guinness Universalist

guinness

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Posted (edited)

Thats just the example i use as its the most often questioned in my head, and really the only magic numbers i use frequently.  Like the first couple of Guiness' posts with $MB_SYSTEMMODAL and thought "umm thats more typing than the digit and no more useful".

As demonstrated in your post mistakes can happen, if for example you have a magic number of "42" spread across multiple source files and it should be 43, then you have a lot of work ahead of you than changing typing a variable name. So time of debugging vs typing a couple extra characters, I know which one wins that war.

Incidentally my username is guinness! 

Edit: I changed one word for better clarity in my point.

Edited by guinness

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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guinness Universalist

guinness

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Posted

I entirely agree with you guinness. Use of magic numbers should be restrited, but not ruled out.

No of course not, but there are limited examples where magic numbers can be deemed acceptable.

boththose read this article: http://en.wikipedia.org/wiki/Magic_number_(programming)

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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AZJIO Universalist

AZJIO

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Posted

verbosity in programming.

You remember thousands reductions? It is necessary to read the reference to look as it is written.

I was also too lazy to write a lot of character

Now any example in the Help file requires UDF

All examples are not compatible with 3.3.8.1

To replace all the numbers - easy: MsgBox(0,   --> MsgBox(43,

My other projects or all

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czardas Universalist

czardas

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Posted (edited)

Some people have made some very interesting comments in this thread.

Mat mentioned earlier about some constants being liable to change so, for the sake of forward compatibility, using globals makes a lot of sense. However this argument seems more a case of damage limitation: because changing constants should really be frowned upon due to backwards incompatibility.

What seems to make this so complicated is the number of unrelated consequences of choosing one method over another. I am of the opinion that you learn less if you do not take things apart and try to probe beneath the surface. I like having choices, but I need to know the consequences of the choices I make. Nobody should feel insulted by this.

To replace all the numbers - easy: MsgBox(0,   --> MsgBox(43,

 

It's easy for a regexp wizzard like you Azjio. :)

Edited by czardas

operator64  ArrayWorkshop

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DatMCEyeBall Universalist

DatMCEyeBall

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I didn't like 0xDEADBEEF so I tried some 0xCABBA6E but it was poisoned so I got a 0xD15EA5E and now I 0xFEE1DEAD.

"Just be fred, all we gotta do, just be fred."  -Vocaliod

"That is a Hadouken. A KAMEHAMEHA would have taken him 13 days and 54 episodes to form." - Roden Hoxha

@tabhooked

Clock made of cursors ♣ Desktop Widgets ♣ Water Simulation

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Mat Universalist

Mat

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Mat mentioned earlier about some constants being liable to change so, for the sake of forward compatibility, using globals makes a lot of sense. However this argument seems more a case of damage limitation: because changing constants should really be frowned upon due to backwards incompatibility.

Lets say you have the file name of the config file for an application, which is "settings.ini". Since the filename is not going to change, and its pretty obvious what it is, there is the temptation to just use "settings.ini" throughout the code.

That's bad practice. Not just because of forward compatibility problems either (which is not likely to be an issue but could be). It's more important that if you make a typo in the string, it's not an error. If you make a typo in a variable it is an error, so you see it straight away.

Same goes for magic numbers as well, if you have flags that start from zero then 1 and 2 are both valid flags with keys next to each other on the keyboard. Accidentally hit 2 instead of 1, and don't immediately notice, the problem won't be apparent just by looking at the code, as you'll see 2+16+64 and it looks like your adding flags. In reality you could have completely changed the behaviour of the program (Edit: Or worse - subtly changed it)

Edited by Mat

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guinness Universalist

guinness

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Posted

I said the same Mat.

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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czardas Universalist

czardas

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  • Author
Posted (edited)

Lets say you have the file name of the config file for an application, which is "settings.ini". Since the filename is not going to change, and its pretty obvious what it is, there is the temptation to just use "settings.ini" throughout the code.

That's bad practice. Not just because of forward compatibility problems either (which is not likely to be an issue but could be). It's more important that if you make a typo in the string, it's not an error. If you make a typo in a variable it is an error, so you see it straight away.

 

This is a good argument, but it is different from saying you use named constants because their values may be changed in the future. Typos are something else. In any case, I would say "settings.ini" does not qualify as a named constant.

Edited by czardas

operator64  ArrayWorkshop

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Mat Universalist

Mat

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Posted

This is a good argument, but it is different from saying you use named constants because their values may be changed in the future. Typos are something else. In any case, I would say "settings.ini" does not qualify as a named constant.

"settings.ini" is a magic string (for want of a better word for it). $SETTINGS_FILE is a named constant.

The latter is nearly always better.

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