BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  "Inherited", "absolute", "Nil" - in Pascal; ?????? - in C++B          BorlandTalk.com Forum Index -> C++ Builder (VCL Components Development) View previous topic :: View next topic   Author Message Serge CSM Guest Posted: Wed Sep 03, 2003 7:15 am    Post subject: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in C++B Hi, I just found a declaration in Paslal (Delphi component source) like: What is inherited I know, but how to call an inherited method in C++Builder? Please give me some sugestions... ------------------- begin ----------------------- procedure TCustomMPHexEditor.Loaded; // where Loaded() is declared as Virtual function begin inherited; CreateEmptyFile(UNNAMED_FILE); end; -------------------- end ------------------------ Second Q: how to translate a nothing pointer var = NIL from Pascal to C++. var = 0 is usable in this case. And one more Q: how to translate ABSOLUTE directive from Pascal to C++Builder. ---------------------- begin --------------------- Value : integer; LCrdTemp: cardinal absolute Value; ----------------------end------------------------ Back to top Ralph Kazemier Guest Posted: Wed Sep 03, 2003 8:39 am    Post subject: Re: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in "Serge CSM" <gunivas (AT) moldovacc (DOT) md> wrote Quote: What is inherited I know, but how to call an inherited method in C++Builder? Please give me some sugestions... C++ does not support the inherited keyword. You must specify the scope of the function yourself. The scope in this case is your base class; void __fastcall TCustomMPHexEditor::Loaded() { baseclass::Loaded(); CreateEmptyFile(UNNAMED_FILE); } I usually declare a type in the class itself, called inherited; class TCustomMPHexEditor: public TComponent { typedef TComponent inherited; public: virtual void __fastcall Loaded(); }; void __fastcall TCustomMPHexEditor::Loaded() { inherited::Loaded(); CreateEmptyFile(UNNAMED_FILE); } Quote: Second Q: how to translate a nothing pointer var = NIL from Pascal to C++. var = 0 is usable in this case. Could you please be more specific? However, in general, NULL (C++) is the equivalent for Nil (Pascal). Quote: And one more Q: how to translate ABSOLUTE directive from Pascal to C++Builder. ---------------------- begin --------------------- Value : integer; LCrdTemp: cardinal absolute Value; ----------------------end------------------------ In the example above, the absolute directive instructs that LCrdTemp uses the same memory space as Value does. In other words, a type-cast. In C++ this could translate to; int Value; Cardinal* LCrdTemp = reinterpret_cast<Cardinal*>(&Value); Ralph Back to top Serge CSM Guest Posted: Wed Sep 03, 2003 9:10 am    Post subject: Re: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in Hi Ralph, Quote: Second Q: how to translate a nothing pointer var = NIL from Pascal to C++. var = 0 is usable in this case. Could you please be more specific? However, in general, NULL (C++) is the equivalent for Nil (Pascal). Ok! It's right. I used = 0 and =NULL. The results was the same in both cases. But the problem is how my code for example will be interpreted by C++Builder 3. Take a look to other definition of Nil: http://www.bridgespublishing.com/articles/issues/9707/Using_Delphi_component s_in_C++Builder.htm Look in chapter "More const issues" and you will se this other definition: --------------------- cut here -------------------------------------------------------- const DefPointer = nil; //Pascal source code This declaration causes C++Builder to generate the following declaration in the header: const void * DefPointer = (void *)(0x0); I don't know why this particular declaration is translated into a const declaration rather than a #define. Perhaps Borland will fix this problem in future versions of C++Builder. For the time being, you can work around it by declaring the constant as follows: const DefPointer = 0; ---------------------- cut here --------------------------- Back to top Ralph Kazemier Guest Posted: Wed Sep 03, 2003 10:18 am    Post subject: Re: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in "Serge CSM" <gunivas (AT) moldovacc (DOT) md> wrote Quote: Take a look to other definition of Nil: [...] The article involves the problems that may arise when C++ Builder compiles Delphi code. In this case header file generation in particular. If you declare a const variable in a Delphi unit; const DefPointer = nil; it will create the following entry in a .hpp file; const void * DefPointer = (void *)(0x0); The article then states; "Although this declaration looks bizarre, the greater sin is that this const declaration appears in a header file." IMO the declaration is not bizarre. It not a sin that the declaration appears in a header file. However, what could cause problems here is that the definition is in the header file, as the article explains; "Let's say you have a project that has multiple source code units. In addition, more than one of those source units #includes the header containing this declaration. The application will compile with no problems, but it will fail at link time, complaining that the variable DefPointer is declared in one unit and again in another unit." Quote: But the problem is how my code for example will be interpreted by C++Builder 3. Your original question was: "how to translate a nothing pointer var = NIL from Pascal to C++.". So, I presume you are porting Delphi code C++ yourself. If so, you have nothing to worry about. Simply declare the variable in a .h file and define it in a .cpp file; ..h: --- extern const void * DefPointer; ..cpp: ----- const void * DefPointer = (void *)(0x0); Doing so, DefPointer is defined only once and thus will not cause linker errors. This is common practice and will compile correctly in BCB1,3,4,5 and 6. Ralph Back to top Serge CSM Guest Posted: Wed Sep 03, 2003 10:47 am    Post subject: Re: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in Thank's Ralph for very good explication! I just read about Delphi to C++ conversion on borland comunity web-site. and found the same info about header creation-translation of Pascal source used by DCC32.EXE of C++Builder pack. See you later... I just finish to print from PDF the book "Borland C++ 6 Developer guide" (1180 pages!!!) and send it to binder. After that "I think!" i'll have a less questions... and don't grab your time. Thank's. Serge. Back to top Ralph Kazemier Guest Posted: Wed Sep 03, 2003 12:28 pm    Post subject: Re: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in "Serge CSM" <gunivas (AT) moldovacc (DOT) md> wrote Quote: I just finish to print from PDF the book "Borland C++ 6 Developer guide" (1180 pages!!!) and send it to binder. Wow! How long did that take? Ralph Back to top Serge CSM Guest Posted: Wed Sep 03, 2003 1:30 pm    Post subject: Re: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in Quote: I just finish to print from PDF the book "Borland C++ 6 Developer guide" (1180 pages!!!) and send it to binder. Wow! How long did that take? Hmmm. About 40-50 min on "HP LaserJet 5000 PS". Book is allready in my hands! Great Book! Check email. Ralph one more Q: ---------------------------------- function TCustomMPHexEditor.GetMouseOverSelection: boolean; var LPntMouse: TPoint; begin Windows.GetCursorPos(LPntMouse); LPntMouse := ScreenToClient(LPntMouse); Result := CursorOverSelection(LPntMouse.x, LPntMouse.y); end; ---------------------------------- I just translated it C++ and get an errror: -------------------------------- bool __fastcall TCustomMPHexEditor::GetMouseOverSelection(void) { TPoint * LPntMouse; ::GetCursorPos(LPntMouse); LPntMouse = ScreenToClient(LPntMouse); // E2064 Cannot initialize 'const TPoint &' with 'TPoint *' //E2342 Type mismatch in parameter 'Point' (wanted 'const TPoint &', got 'TPoint *') E2034 Cannot convert 'TPoint' to 'TPoint *' return CursorOverSelection(LPntMouse.X, LPntMouse.Y); //E2294 Structure required on left side of . or .* } ----------------------------- Where is my mistake? I can undestand in what cases I must use?: 1. TPoint * LPntMouse; 2. TPoint LPntMouse; 3. LPntMouse = new TPoint(this) Back to top Ralph Kazemier Guest Posted: Wed Sep 03, 2003 1:58 pm    Post subject: Re: "Inherited", "absolute", "Nil" - in Pascal; ?????? - in "Serge CSM" <gunivas (AT) moldovacc (DOT) md> wrote Quote: I just translated it C++ and get an errror: [...] Quote: TPoint * LPntMouse; ::GetCursorPos(LPntMouse); You pass an uninitialized pointer to GetCursorPos() here. You should either dynamically allocate memory; TPoint * LPntMouse = new TPoint; ::GetCursorPos( LPntMouse ); ... delete LPntMouse; or just pass the address of a TPoint; TPoint LPntMouse; ::GetCursorPos( &LPntMouse ); The latter is probably best, since you won't have to concern yourself with memory (de)allocation. Besides you need a TPoint futher on anyway ;) Quote: LPntMouse = ScreenToClient(LPntMouse); // E2064 Cannot initialize 'const TPoint &' with 'TPoint *' The compiler tries to create a temporary TPoint object for you, but fails since TPoint does not have a constructor taking an TPoint* as parameter. Quote: //E2342 Type mismatch in parameter 'Point' (wanted 'const TPoint &', got 'TPoint *') E2034 Cannot convert 'TPoint' to 'TPoint *' ScreenToClient() expects a TPoint& (reference to TPoint). You pass a TPoint*. That is the 'Type mismatch'. Furthermore, the compiler tries to implicitly cast TPoint to TPoint*, but fails. Quote: return CursorOverSelection(LPntMouse.X, LPntMouse.Y); //E2294 Structure required on left side of . or .* } Since you have declared LPntMouse as TPoint*, the compiler complains about the fact you should use it as a pointer, e.g.; LPntMouse->X or LPntMouse.*X To sum it up, change the function to; bool __fastcall TCustomMPHexEditor::GetMouseOverSelection() { TPoint LPntMouse; ::GetCursorPos( &LPntMouse ); LPntMouse = ScreenToClient( LPntMouse ); return CursorOverSelection(LPntMouse.X, LPntMouse.Y); } Ralph Back to top Serge CSM Guest Posted: Wed Sep 03, 2003 2:13 pm    Post subject: Re: TPoint structure Hi Ralph, Just found in the book: Quote: return CursorOverSelection(LPntMouse.X, LPntMouse.Y); All is perfect only one little mistake here: return CursorOverSelection(LPntMouse.y, LPntMouse.y) TPoint structure is quite diferent from other structures like TGridCoord for example. (Why bordand made this, why he used lower- and upper case leters for coordinates XY). There must be used lowercase leters ".x" and ".y". All done. Thank's Serge. Back to top Serge CSM Guest Posted: Thu Sep 04, 2003 6:56 am    Post subject: Re: Inherited again Quote: Hi Ralph, I'm finishing my component but got some Q that I never found prior: 1. How to understand (translate) next code: -------------------------------------- procedure TCustomMPHexEditor.Loaded; begin inherited; // <- ???? CreateEmptyFile(UNNAMED_FILE); end; ------------------------------------- 2. And this code: --------------------------------------------------- procedure TCustomMPHexEditor.Resize; begin PostMessage(Handle, WM_INTUPDATECARET, 7, 7); inherited; end; --------------------------------------- What is the differense between first and second declaration? Thank's. Serge. P.S. Waiting for you mail.... Back to top Remy Lebeau (TeamB) Guest Posted: Thu Sep 04, 2003 7:41 am    Post subject: Re: Inherited again "Serge CSM" <gunivas (AT) moldovacc (DOT) md> wrote Quote: 1. How to understand (translate) next code: -------------------------------------- procedure TCustomMPHexEditor.Loaded; begin inherited; // <- ???? CreateEmptyFile(UNNAMED_FILE); end; Ralph already gave you that exact answer in his first reply. Please do back and have another look at his examples. Gambit --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system ([url]http://www.grisoft.com)[/url]. Version: 6.0.515 / Virus Database: 313 - Release Date: 9/1/03 Back to top Serge CSM Guest Posted: Thu Sep 04, 2003 7:59 am    Post subject: Re: Inherited again Hi Gambit, Quote: Ralph already gave you that exact answer in his first reply. Please do back and have another look at his examples. You did not undestand me... What is the differense between calling "inherited" before and after calling procedure. Or: What is a diference between calling process of Example 1 and Example 2 in Pascal: 1. inherited; // <- ???? CreateEmptyFile(UNNAMED_FILE); 2. CreateEmptyFile(UNNAMED_FILE); inherited; This procedures are equivalent? Back to top Remy Lebeau (TeamB) Guest Posted: Thu Sep 04, 2003 5:12 pm    Post subject: Re: Inherited again "Serge CSM" <gunivas (AT) moldovacc (DOT) md> wrote Quote: What is the differense between calling "inherited" before and after calling procedure. There is no difference in the calls themselves. They both do the exact same thing - invoke the base class functionality. When you choose to actually do that is not important unless you are writing code that depends on the result of the base class handling, or you simply do not want the base class to handle the operation until after you have first. Gambit --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system ([url]http://www.grisoft.com)[/url]. Version: 6.0.515 / Virus Database: 313 - Release Date: 9/1/03 Back to top Timothy H. Buchman Guest Posted: Tue Sep 09, 2003 4:33 pm    Post subject: Re: Inherited again Ralph Kazemier <ralph (AT) kazemier (DOT) demon.nl> wrote Quote: That is the difference It depends on what the inherited function does really. Have a look at the following example; FYI, it might be good practice to avoid this kind of design. Users of the class X might be wondering (just like you are) how to call the inherited function. In the following example there is no need to call the inherited function at all; It doesn't reflect badly at all on Ralph's excellent discussion to observe for Serge's benefit that there are, at the very least, cases in the Borland VCL where it is essential to call inherited functions. These include overridden methods of components, particularly Events that subsequent user's of the derived component have the option of supplying their own event handler for. As Ralph points out, the location of the inherited:: call often determines whether the user's code has the intended effect. -- Timothy H. Buchman ======================================== City Center Theater, New York NY mail address tbuchmanPLEASE(at sign)REMOVEcitycenter.org Search .borland message archive on http://www.mers.com/searchsite.html 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 (VCL Components Development) All times are GMT Page 1 of 1   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.