BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  EditBox and Float          BorlandTalk.com Forum Index -> C++ Builder (Language C++) View previous topic :: View next topic   Author Message Renan Guest Posted: Mon Jul 17, 2006 10:37 pm    Post subject: EditBox and Float My code: void __fastcall TNovaMistura::Button3Click(TObject *Sender) { float a11, a12, total; a11 = StrToFloat(Edit11->Text); a12 = StrToFloat(Edit12->Text); total = StrToFloat(Edit31->Text); a11 = a11/100; a12 = a12/100; Edit21->Text = FloatToStr(a11*total); Edit22->Text = FloatToStr(a12*total); } } Edit21 always gets numbers like these: 16,555666 I want to set it to only 2 units after coma : 16,56 (I don't know if your gonna understand what I have sad, but if don't, I will try again.) And also if you have suggestions about how to optimize the code. Renan Back to top Darío Alejandro Guzik Guest Posted: Tue Jul 18, 2006 12:26 am    Post subject: Re: EditBox and Float Hi! When working with floating point numbers you have to be carefull because not all real numbers are representable with floating point numbers. In those cases the number stored in the float variable will be the floating point number that is the closest to the number you wanted to store. If you want to show the number rounded to 2 decimals you could use FloatToStrF, but have in mind that the number you show is not the number you have stored. If you want to work with numbers having only 2 decimal places, I would recommend NOT using float or doubles. Renan wrote: Quote: My code: void __fastcall TNovaMistura::Button3Click(TObject *Sender) { float a11, a12, total; a11 = StrToFloat(Edit11->Text); a12 = StrToFloat(Edit12->Text); total = StrToFloat(Edit31->Text); a11 = a11/100; a12 = a12/100; Edit21->Text = FloatToStr(a11*total); Edit22->Text = FloatToStr(a12*total); } } Edit21 always gets numbers like these: 16,555666 I want to set it to only 2 units after coma : 16,56 (I don't know if your gonna understand what I have sad, but if don't, I will try again.) And also if you have suggestions about how to optimize the code. Renan -- Darío Alejandro Guzik (El Tío Borracho) http://tioborracho.tripod.com e-mail: daguzik (AT) dc (DOT) uba.ar ICQ : 8389493 Back to top Remy Lebeau (TeamB) Guest Posted: Tue Jul 18, 2006 12:27 am    Post subject: Re: EditBox and Float "Renan" <gulbrrs (AT) gmail (DOT) com> wrote in message news:44bbcae0$1 (AT) newsgroups (DOT) borland.com... Quote: Edit21 always gets numbers like these: 16,555666 I want to set it to only 2 units after coma : 16,56 Look at FormatFloat() Gambit Back to top MrT Guest Posted: Tue Jul 18, 2006 6:31 am    Post subject: Re: EditBox and Float Darío Alejandro Guzik wrote: Quote: Hi! When working with floating point numbers you have to be carefull because not all real numbers are representable with floating point numbers. In those cases the number stored in the float variable will be the floating point number that is the closest to the number you wanted to store. If you want to show the number rounded to 2 decimals you could use FloatToStrF, but have in mind that the number you show is not the number you have stored. If you want to work with numbers having only 2 decimal places, I would recommend NOT using float or doubles. And what would you suggest? Quote: Renan wrote: My code: void __fastcall TNovaMistura::Button3Click(TObject *Sender) { float a11, a12, total; a11 = StrToFloat(Edit11->Text); a12 = StrToFloat(Edit12->Text); total = StrToFloat(Edit31->Text); a11 = a11/100; a12 = a12/100; Edit21->Text = FloatToStr(a11*total); Edit22->Text = FloatToStr(a12*total); } } Edit21 always gets numbers like these: 16,555666 I want to set it to only 2 units after coma : 16,56 (I don't know if your gonna understand what I have sad, but if don't, I will try again.) And also if you have suggestions about how to optimize the code. Renan Back to top Thorsten Kettner Guest Posted: Tue Jul 18, 2006 1:29 pm    Post subject: Re: EditBox and Float "Renan" <gulbrrs (AT) gmail (DOT) com> wrote: Quote: float a11, a12, total; a11 = StrToFloat(Edit11->Text); a12 = StrToFloat(Edit12->Text); total = StrToFloat(Edit31->Text); a11 = a11/100; a12 = a12/100; Edit21->Text = FloatToStr(a11*total); Edit22->Text = FloatToStr(a12*total); Floating point variables are not precise, but only approximating the actual value. If you want to use floating point types though, then use double instead of float. It uses some bytes more for storing the value and is thus more precise. (There is even the type long double available, but not all available functions support that type). When displaying floating point values, always format the output (with FormatFloat for instance). If you stay in the range of up two four decimal places and want more accuracy then you could use Currency as a fixed point type: Currency a11, a12, total; a11 = StrToCurr(Edit11->Text); If you even need more precision then look out for a so-called rational library. Back to top Darío Alejandro Guzik Guest Posted: Tue Jul 18, 2006 7:30 pm    Post subject: Re: EditBox and Float MrT wrote: Quote: Darío Alejandro Guzik wrote: Hi! When working with floating point numbers you have to be carefull because not all real numbers are representable with floating point numbers. In those cases the number stored in the float variable will be the floating point number that is the closest to the number you wanted to store. If you want to show the number rounded to 2 decimals you could use FloatToStrF, but have in mind that the number you show is not the number you have stored. If you want to work with numbers having only 2 decimal places, I would recommend NOT using float or doubles. And what would you suggest? It deppends on what are you doing. Another user recommended Currency, I would recommend just using ints. It all deppends on your needs. I didn't lok for it but there must be dozens of fixed point numbers classes for c++ around. -- Darío Alejandro Guzik (El Tío Borracho) http://tioborracho.tripod.com e-mail: daguzik (AT) dc (DOT) uba.ar ICQ : 8389493 Back to top Thorsten Kettner Guest Posted: Wed Jul 19, 2006 7:30 pm    Post subject: Re: EditBox and Float "Renan" <gulbrrs (AT) gmail (DOT) com> wrote: Quote: I did use FloatToStrF, It works for what I'm trying to do. float a11, a12, total; a11 = StrToFloat(Edit11->Text); a12 = StrToFloat(Edit12->Text); total = StrToFloat(Edit31->Text); a11 = a11/100; a12 = a12/100; Edit21->Text = FloatToStrF(a11*total,ffFixed,6,2); Edit22->Text = FloatToStrF(a11*total,ffFixed,6,2); Okay. As you mention in another thread that you are a beginner, please notice: the word "Float" in StrToFloat and FloatToStrF mean "floating point variable", not necessarily a float. It is even so that the type float is rarely the appropriate type. As mentioned, floating point vars are inaccurate. There are three types available: float (4 bytes) precison = 7 digits double (8 bytes) precision = 15 digits long double (80 bits) precision = 18 digits As the values are stored approximated, would you be ready to lose precision, just to save 4 bytes? I wouldn't usually. There are functiuons that don't support long double, so I usually use double, but never float. Back to top MrT Guest Posted: Mon Aug 21, 2006 6:30 am    Post subject: Re: EditBox and Float Hi: Why is mynposting in this thread: Error! newsgroup server responded:no such article number in this group Perhaps the article has expired <44bc39a1$1 (AT) newsgroups (DOT) borland.com> (46102) Remy Lebeau (TeamB) wrote: Quote: "Renan" <gulbrrs (AT) gmail (DOT) com> wrote in message news:44bbcae0$1 (AT) newsgroups (DOT) borland.com... Edit21 always gets numbers like these: 16,555666 I want to set it to only 2 units after coma : 16,56 Look at FormatFloat() Gambit 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 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.