BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  number of elements in a enum Goto page 1, 2  Next          BorlandTalk.com Forum Index -> C++ Builder (Language C++) View previous topic :: View next topic   Author Message masi Guest Posted: Wed Feb 15, 2006 3:03 pm    Post subject: number of elements in a enum Is there a way to know, programmatically, the number of the elements in an enumeration, id est: enum {first, second , third}; how can I know that the enumeration has three elements? I usually do the following: enum {first, second , third, number_of_elements}; so I know that number_of_elements contains the number of the elements in the enumeration. Thanks, masi urbano Back to top Thomas Maeder [TeamB] Guest Posted: Wed Feb 15, 2006 3:03 pm    Post subject: Re: number of elements in a enum "masi" <masiurb (AT) tin (DOT) it> writes: Quote: Is there a way to know, programmatically, the number of the elements in an enumeration, id est: enum {first, second , third}; how can I know that the enumeration has three elements? By looking at the definition :-) Quote: I usually do the following: enum {first, second , third, number_of_elements}; so I know that number_of_elements contains the number of the elements in the enumeration. So do I. Is there a problem with this approach? Back to top Liz Albin Guest Posted: Wed Feb 15, 2006 3:03 pm    Post subject: Re: number of elements in a enum On Wed, 15 Feb 2006 15:10:00 +0100, masi wrote: Quote: Is there a way to know, programmatically, the number of the elements in an enumeration, id est: Why do you want to know? There may be some other construct that helps you do what you'd like. -- liz Back to top Alan Bellingham Guest Posted: Wed Feb 15, 2006 3:03 pm    Post subject: Re: number of elements in a enum "masi" <masiurb (AT) tin (DOT) it> wrote: Quote: Is there a way to know, programmatically, the number of the elements in an enumeration, id est: enum {first, second , third}; You can't. An enumeration doesn't contain elements - it declares items. There is no detectable difference between enum {first, second , third}; and enum {first = 0}; enum {second = first+1}; enum {third = second+1}; Quote: how can I know that the enumeration has three elements? I usually do the following: enum {first, second, third, number_of_elements}; so I know that number_of_elements contains the number of the elements in the enumeration. That fails totally the moment you go enum {first = -3, second, third, number_of_elements}; as the final value ends up being 0! But, so long as you let the enumeration start from zero, and do not explicitly set any of the other members, then the method you are using is the best I know. Alan Bellingham -- ACCU Conference 2006 - 19-22 April, Randolph Hotel, Oxford, UK Back to top masi Guest Posted: Wed Feb 15, 2006 4:03 pm    Post subject: Re: number of elements in a enum Thanks to all. My idea was to avoid things as: #define SOMEWHAT 0 #define SOMEWHATELSE 1 #define SOMEWHATXXX 2 #define NUM_CONSTS 3 I have arrays declared as int vect[NUM_CONSTS]; and I usually iterate on them doing: for (int i=0; i<NUM_CONSTS; i++){ DoSomeThingWith(vect[i]); } but: everytime I had to suppress or add a #define I have to rearrange many of the elements, that's why the idea of using: enum{ SOMEWHAT, SOMEWHATELSE, SOMEWHATXXX, NUM_CONSTS }; thanks again masi urbano Back to top Liz Albin Guest Posted: Wed Feb 15, 2006 4:03 pm    Post subject: Re: number of elements in a enum On Wed, 15 Feb 2006 16:03:00 +0100, masi wrote: Quote: int vect[NUM_CONSTS]; and I usually iterate on them doing: for (int i=0; i<NUM_CONSTS; i++){ DoSomeThingWith(vect[i]); } Perhaps you should look at std::vector. -- liz Back to top Chris Uzdavinis (TeamB) Guest Posted: Wed Feb 15, 2006 4:03 pm    Post subject: Re: number of elements in a enum "masi" <masiurb (AT) tin (DOT) it> writes: Quote: Is there a way to know, programmatically, the number of the elements in an enumeration, id est: enum {first, second , third}; how can I know that the enumeration has three elements? In the general case, you simply cannot. You're declaring enumerators to have specific values. In the above example, the values start at zero and count up sequentially from there. Quote: I usually do the following: enum {first, second , third, number_of_elements}; so I know that number_of_elements contains the number of the elements in the enumeration. That's the only way to do it, except that it depends on the fact that you do not change the values of the enumerators. -- Chris (TeamB); Back to top masi Guest Posted: Wed Feb 15, 2006 5:03 pm    Post subject: Re: number of elements in a enum Quote: int vect[NUM_CONSTS]; and I usually iterate on them doing: for (int i=0; i<NUM_CONSTS; i++){ DoSomeThingWith(vect[i]); } Perhaps you should look at std::vector. Which are the advantages in using std::vector? masi urbano Back to top Chris Uzdavinis (TeamB) Guest Posted: Wed Feb 15, 2006 5:03 pm    Post subject: Re: number of elements in a enum "masi" <masiurb (AT) tin (DOT) it> writes: Quote: ok, but why if I do: typedef enum{ SOMEWHAT, SOMEWHATELSE, SOMEWHATXXX, }ENUMERATION; I can't access the number of elements? It is an information available to the compiler! I'd like a thing like, say, sizeof(ENUMERATION). Sizeof(ENUMERATION) will tell you the storage requirement to hold a single value. What you're really asking for is not part of the language, and you have to simulate it within the rules that the language does offer. -- Chris (TeamB); Back to top masi Guest Posted: Wed Feb 15, 2006 5:03 pm    Post subject: Re: number of elements in a enum ok, but why if I do: typedef enum{ SOMEWHAT, SOMEWHATELSE, SOMEWHATXXX, }ENUMERATION; I can't access the number of elements? It is an information available to the compiler! I'd like a thing like, say, sizeof(ENUMERATION). merci Back to top Vladimir Stefanovic Guest Posted: Wed Feb 15, 2006 5:03 pm    Post subject: Re: number of elements in a enum Quote: My idea was to avoid things as: #define SOMEWHAT 0 #define SOMEWHATELSE 1 #define SOMEWHATXXX 2 #define NUM_CONSTS 3 Besides using std::vector you may think of: // for string elements ... AnsiString StringElements[] = { "One", "Two", "Three", "Four" }; int StringElementsCount = ( sizeof( StringElements ) / sizeof( AnsiString ) ); ShowMessage( StringElementsCount ); // for integer elements ... int IntegerElements[] = { 1, 2, 3, 4 }; int IntegerElementsCount = ( sizeof( IntegerElements ) / sizeof( int ) ); ShowMessage( IntegerElementsCount ); -- Best regards, Vladimir Stefanovic Back to top Gillmer J. Derge [TeamB] Guest Posted: Wed Feb 15, 2006 6:03 pm    Post subject: Re: number of elements in a enum Chris Uzdavinis (TeamB) wrote: Quote: What you're really asking for is not part of the language, and you have to simulate it within the rules that the language does offer. You and Thomas made that integer-like template a while back. Could that be extended and/or adapted to make an enum-like type that solves some of the common gripes about enums? For example, I'm thinking of: * easy conversion to and from the symbolic name * get a count or maximum value * easily create flag values defined as powers of 2 without manually specifying the values What, if any, features do real enums support that a class like this wouldn't? -- Gillmer J. Derge [TeamB] Back to top masi Guest Posted: Wed Feb 15, 2006 6:03 pm    Post subject: Re: number of elements in a enum Quote: * easily create flag values defined as powers of 2 without manually specifying the values that would be very interesting! Back to top Rudy Velthuis [TeamB] Guest Posted: Wed Feb 15, 2006 7:03 pm    Post subject: Re: number of elements in a enum At 15:38:39, 15.02.2006, Alan Bellingham wrote: Quote: "masi" <masiurb (AT) tin (DOT) it> wrote: Is there a way to know, programmatically, the number of the elements in an enumeration, id est: enum {first, second , third}; You can't. An enumeration doesn't contain elements - it declares items. An enumeration does EXACTLY the same in Delphi (although it is stricter - they are not assignment compatible with integers and other ordinal types), and yet I can specify Low(TheEnumType) and High(TheEnumType), where the compiler will return, as plain literals, first and third, respectively. I guess there is no such thing in C++? -- Rudy Velthuis [TeamB] http://rvelthuis.de/ "It's not that I'm afraid to die, I just don't want to be there when it happens." -- Woody Allen, From 'Death' 1975. Back to top Alan Bellingham Guest Posted: Wed Feb 15, 2006 7:03 pm    Post subject: Re: number of elements in a enum "Rudy Velthuis [TeamB]" <velthuis (AT) gmail (DOT) com> wrote: Quote: You can't. An enumeration doesn't contain elements - it declares items. An enumeration does EXACTLY the same in Delphi (although it is stricter - they are not assignment compatible with integers and other ordinal types), and yet I can specify Low(TheEnumType) and High(TheEnumType), where the compiler will return, as plain literals, first and third, respectively. I guess there is no such thing in C++? No, because C (and thus C++) are not as you describe. In C, with the examples previously given, you'd have to use Low() and High() ... there is no name for the enumeration. A little bit difficult, I think you'd agree. In many ways, it'd be nice to have a better type of enum, but then it'd then fail by not being "assignment compatible with integers and other ordinal types)". It's the very flexibility in C (and C++) that also brings certain shortcomings. The ability to use drop almost any old values into an enumeration type is much of what makes it so powerful, but that same power also means you can't actually really know what the maximum value will be. For example: enum Colour { Black = 0, Red = 1, Green = 2, Blue = 4 }; Colour c = (Red | Green | Blue); gives a legal enumeration type that contains a valid value higher than the highest value actually enumerated. Sure, we could do: enum Colour { Black = 0, Red = 1, Green = 2, ..., Blue = 4, ..., White = 7 }; but it tends to get very messy very fast once you go beyond a tiny handful of bits. Alan Bellingham -- ACCU Conference 2006 - 19-22 April, Randolph Hotel, Oxford, UK Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> C++ Builder (Language C++) All times are GMT Goto page 1, 2  Next Page 1 of 2   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.