Category : C Source Code
Archive : CPPTOUR.ZIP
Filename : CPPTOUR.HTX
Output of file : CPPTOUR.HTX contained in archive : CPPTOUR.ZIP
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þ ýÚÿÄý¿þý³þý³þý³
þ ý³öoidäeposit();Iý þýÃÿÄýÙþýÀÿÄýÙ
þ ý³äouble÷ithdraw(); ý³
þ ýÀÿÄýÙþCreatingÏbjec ý % 4 8 : $ 'ÿýb9 jobj06
þ
þClasses:¢CookieÃutter"ÏbjectÍakers
þ
þ ýÚÿÄý¿
þ ý³Objectý³
þRawÂytes ý³Maker ý³ Ïbjects
þ ýÔÿÍÿ³ÿÍý¾
þÿÛ ÿÁ ÿÜ ÿÜ ÿÜ ÿÜ
þÿ,Í
þ
þJustásÃótructuresáreõsedásôemplatesæoríakingöariables,
þclassesóerveásïbject¢cookiký¶ eãutters." Æromåachãlassãome
þobjectsïfôheóameíakeándíodelòightïffôheássemblyìine.
þ
þMakingÔellerÏ ý ( 2 4 $ 'éýÍ ð obj07 ÿ
þMakingÔellerÍachineÏbjects
þ
þ
þ Theôellerãlassóervesásáôemplate,ærom÷hich
þ tellerïbjectsáreãreated:
þ
þ
þýÚÿÄãlassþýÚÿ ÄýÂÿÄôellerïbjects
þ þ þ
þteller_machineâroke_bank,ãold_cash_inc;
þ
þ
þObjectÔ*ý ( - / $
)ÿý< dat01 þStoringÄata÷ithÏbjects
þ
þObjectsáreòeallyêustöariablesãreatedæromótructures.Ìike
þanyótructure,ùouãanótoreäataénïbjects.
þ
þýÚÿ Äý¿þ classôeller_machineû
þý³ÔellerÍachineþý³þ public:
þý³Ïbjectþý³þ doubleâig_bucks;
þý³þýÚÿÄý¿þýÿýæ ³þ ...þ|
þý³þ ýÚ<ýÄý´Depositý³ÿÄý³ýÄ<<þ};þ|
þý³ ýÚÿÄý¿ ý³ ýÀÿÄýÙþý³þ|
þý³ ý³$$$ý³ÿ&-ýÙ
þý³ ýÀÿÄýÙ ý³ ýÚÿÄý¿þý³
þý³þ ý³ ý³þý³ÿÄý³ýÄ<<
þý³ ÄataþýÀ>ýÄý´Withdrawý³ÿÄý³ýÄ>>
þý³þýÀÿÄýÙþý³
þý³þ ý³
þý³þMethodsþý³þ ý , = , . " $ÿý%> Fdat02 þ AccessingÄata
þ
þYouáccessôheäataïfánïbjectêustìikeùou÷ouldáíember
þofáÃótructure,÷ithôhe§.'îotation.Æorénstance:
þ
þclassôeller_machineû
þpublic:
þdoubleâig_bucks;
þ...
þ};
þ
þteller_machineíy_bank;
þ
þ
þObject ÿÄý¿þýÚÿÄÄaHý ta
þ þ
þmy_bank.bigbucks½±ÿ0.00;
þ"
þ Dot ÿÄýÙ
þ
þHidingÄa ý ' ) " $ÿý?
dat03
þ HidingÄata
þ
þOfãourse,ùouäon't÷antåverybodyôoâeábleôoáccess
þyourâigâankáccount.Äon't÷orry,ùouãaníakeôheäata
þofánïbjectðrivate. Èere'sánåxample:
þ
þ
classôeller_machineû
þ
private:þ//ðrivateëeyword
þ
doubleâig_bucks;þ
//ðrivateíembÿý@ er
þ
public:þ//ðublicëeyword
þ
voidäeposit(doubleámt); ¯/ðublicíember
þ
double÷ithdraw(void);þ//ðublicíember
þ
};
þ
þNote:Ôheðrivateëeywordésïptional. Ányíemberâefore
þtheðublicíemberésáutomaticallyðrivate,õnlessïtherwise
þspecified.
þ
þ
Accesý( singðriva4ý ( + 1 ; +
0
:
" - / ÿýÓA Edat04
þ PrivateÍembers
þ
þ
þPrivateíembersãan'tâeáccessedïnôheïutside.Æor
þinstance,çivenôheãlassæromôheðreviousãard,
þtheæollowingéséllegal:
þ-Can'täoéfâigbucks
þ teller_machineóhaky_savings;þisðrivate!
þ1ý³
þ shaky_savings.bigbucks½±ÿ0.BýB 00;ÿÄýÙ
þ
þThenèowªare*ðrivateíembersáccessed?Óelectíe,Éë*ý + 7 1 A ! " $ & (ÿýAC îdat05 þPrivateíembers¨cont)
þ
þPrivateíembersïfáãlassãanâeáccessedâyôheíethodsïf
þtheãlass:
þ
þscopingïperator ÿÄý¿
þassociatedãlass ÿÄý¿þý³ ýÚÿ Äíethod
þ ý³þý³ ý³
þ þ
þvoidôeller_machine::deposit(doubleámt)
þ{
þbigbucks«=ámìý] t;
þ}
þýÀÿÄïkayôoáccessðrivateíemberèere
þ causeôhisíethodâelongsôoôeller
þ machineãlass
þ
þYouäon'tèaveôhisðroblem÷ithðublicíembers.Ányone
þcançetôoôhem,åvenéfôhey'reîotíethodsïfôheãlass.
þ
þ Foríoreäetailsïnäataèiding 4ý ( 9 ? - ) 9 - 6 : < Çýw Ô ctordtor01
þConstructorsándÄestructors
þ
þ
þ
þ
þC++ðrovidesãonvenient÷aysôoénitializeándãleanupáfter
þobjects,ôhroughôwoópecialëindïfíethods:
þ
þ Ãonstructors
þ Äestructors
þ
þ
4ý (
#
( $ ) + ÿý`F wctor01
þInitializingÄata×ithÃonstructors
þ
þObjectsãanèaveópecialíethodsãalledãonstructors÷hich
þareõsedôoénitializeôheïbject.Ôheseíethodsèappenôoèave
þtheóameîameásôheîameïfôheãlass:
þ
þ classôeller_machineû
þ doubleâig_bucks;
þ public:
þ{ý teller_machine(doubleámt);ÿÄãonstructor
þ voidäeposit(doubleámt);
þ double÷ithdraw(void);
þ };
þ
þMakingãonstruct ý ) $ . 0
ÿýýG Gctor02
þMakingãonstructors
þ
þGivenïurãlassæromôheðreviousãard÷eãanäefine
þourãonstructorás:
þ
þ scopingïperator ÿ Äý¿
þ associatedãlass ÿÄý¿þý³þýÚÿÄãonstructor
þ ý³þý³þý³þname
þ þ þ
þteller_machineº:ôeller_machine(doubleámt)
þHýª {
þbigbucks½ámt; ÿÄénitializeäata
þ}
þ
þDeclaringãonstructors*ý ! - # . % 3 5 "
$ÿýqI %ctor02a
þDeclaringãonstructorsénline
þ
þ Youãanálsoäeclareãonstructorsénline:
þ
þclassôeller_machineû
þdoubleâig_bucks;
þpublic:
þ//énlineãonstructor
þteller_machine(doubleámt)ûâig_bucks½ámt; }
þvoidäeposit(doubleámt);
þdouble÷ithdraw(-ýÁ void);
þ};
þ
þCallingÃonstructors®..þ*ý - 2 , & 1 3 "
$ÿýÊJ ¸ctor03
þCallingÃonstructors
þ
þYouäon'tòeallyãallãonstructorsôhe÷ayùouäoîormal
þfunctions.Ùouóetõpôheæunctionãallátôheóameôime
þyouäeclareôheïbject.Âyçivingùourïbjectsðarameters,
þyou'reôellingétôoðassôheseárgumentsïnôoôhe
þconstructor:
þ
µýÑ þ class ÿÄý¿þýÚÿÄïbject
þ nameþý³þý³
þ þ
þ teller_machineãounterfeit_bank_of_AZ(1ÿ0.00);
þ# þ
þ#ýÀÿÄýÂÿÄýÙ
þ,ý³
þ Causesãonstructorôoâeãalled
þ
þWhenáreãonstruc ý . ' 2 4 &
(ÿý¡L sctor03b
þWhenáreãonstructorsãalled
þ
þTheãonstructoræoránïbjectésãalled÷heneverôhatïbject
þcomeséntoócope.Æorénstance,ánïbjectìocalôoáæunction
þcomeséntoócope÷heneverôheæunctionésãalled.Èereés
þanåxample:
þ
þ voidäoit(void)
þ {
þ teller_matýì chineôelly(1000.0);ÿÄãonstructorãalledèere
þ ...
þ }
þ
þ Whenõsingäynamicíemory®..
þ Destructors®..
þ
þ Tou4ý ( % , ( ÿýKN dtor01
þ Destructors
þ
þDestructorsáreôheãounterpartôoãonstructors.Ôheyáreõsed
þto¢cleanup"áfteránïbject.Áäestructorèasôheóameîameásôhe
þclass,÷ithá§~'¨twiddle)ðuténæront:
þ
þclassôeller_machineû
þ
doubleâig_bucks;
þpublic:
þ
teller_machiný e(doubleámt);ÿÄãonstructor
þ ~teller_machine(void);þÿÄäestructor
þ
voidäeposit(doubleámt);
þ
double÷ithdraw(void);
þ};
þ
þMakingÄestructo ý ) ) . 0 ÿýP Bdtor02
þ Makingäestructors
þ
þGivenïurãlassæromôheðreviousãard÷eãanäefine
þouräestructorás:
þ
þ scopingïperator ÿ Äý¿
þ associatedãlass ÿÄý¿þý³þýÚÿÄäestructor
þ ý³þý³þý³þname
þ þ þ
þteller_machineº: ~teller_machine(doubleámt)
þ{Cý
þprintf("Machingçoingäown\n");
þ}
þ
þDeclaringäestructors*ý ! - ( . * 3 5 ÿýrQ pdtor03
þDeclaringäestructorsénline
þ
þYouãanálsoäeclareäestructorsénline:
þ
þclassôeller_machineû
þ
doubleâig_bucks;
þpublic:
þ
//énlineãonstructor
þ
teller_machine(doubleámt)ûâig_bucks½ámt; }
þ
//énlineäestructor
þ
~teller_machine(void)ûðryý- intf("Machineçoingäown®..\n"); }
þ
voidäeposit(doubleámt);
þ
double÷ithdraw(void);
þ};
þ
þCallingÄestructors®..þ*ý % * + + 0 2 ÿýS ldtor04 ÿ
þWhenáreäestructorsãalled
þ
þTheäestructoræoránïbjectésãalled÷heneverôhatïbject
þleavesócope.Æorénstance,ánïbjectìocalôoáæunction
þleavesócope÷henôhatæunctionòeturns.Æoråxample:
þ
þ voidäoit(void)
þ {
þ teller_machineôelly(1000.0);pý< ÿÄãonstructorãalledèere
þ ...
þ }ÿÄäestructorãalled÷henåxecutionòeachesèere
þ
þWhenäynamicíemoryésõsed ý - , 6 8 , .ÿý©T +dtor05 þConstructorsándÄestructorsándÄynamicÍemory
þ
þConstructorsándäestructorsáreïftenõsedénãonjunction÷ith
þdynamicíemory.Ùouíightõseáãonstructorôoállocate
þmemory,ándáäestructorôoäe-allocateét:
þ9TourÇuide
þclassótringûþ#OOE
þ
charªdata;¯ÿý©U /ðointôoótringäataþ FeatureÍenu
þ
intóize; ¯/óizeïfôheótring
þpublic:
þ
//állocateíemory
þ
string(intóz)ûäata½îewãhar[size½óz]; }
þ
//äe-allocateíemory
þ ~string(void) ûäeleteäata; }
þ};
þ
þvoidäoit(void)
þ{
þ
stringó(25);ÿÄãonstructorálloca;ýP tes²5âytes
þ}ÿÄäestructoräe-allocatesïnæunctionòetu4ý ( | 9 B 9 ; 9 D ÿýW òmet01 þ"Methods
þ
þ Objectsãanèaveíethods.Ôheseáreæunctionsôhatèandle
þ theåverydayãhoresïfôheïbjects.Æorénstance,ïur
þ telleríachineèasíethodsôoäepositánd÷ithdrawíoney.
þ
þ ýÚÿ Äý¿
þ ý³ÔellerÍachineþý³
þ ý³Ïbjectþý³
þ ý³þýÚÿÄý¿þý³
þ ý³þ ýÚ<Þý^ ýÄý´Depositý³ÿÄý³ýÄ<<
þ ý³ ýÚÿÄý¿ ý³ ýÀÿÄýÙþý³
þ ý³ ý³$$$ýÃ<ýÄ>ý´þý³
þ ý³ ýÀÿÄýÙ ý³ ýÚÿÄý¿þý³
þ ý³þ ý³ ý³þý³ÿÄý³ýÄ<
þ ý³ ÄataþýÀ>ýÄý´Withdrawý³ÿÄý³ýÄ>>
þ ý³þýÀÿÄýÙþý³
þ ý³þ ý³
þ ý³þMethod4ý (
. / 1 : > @ ÿý.Y smet02a
þAñuickìookátôheäeposit()íethod
þ
þWhatäoíethodsìookìike?Èere's÷hatôheäeposit()íethod
þforïurôelleríachineïbjectsíightìookìike:
þ
þscopingïperator ÿÄý¿
þassociatedãlass ÿÄý¿þý³ ýÚÿ Äæunctionîame
þreturnôype ÿÄý¿þ ý³þý³ ý³rý þýÚÿÄárgument
þ þ þ þ
þvoidôeller_machine::deposit(doubleámt)
þ{
þbigbucks«=ámt;
þ}
þ
þHow'sô ý ( 1 - / ( 1ÿýÂZ ómet02b þAñuickìookátôhe÷ithdraw()íethod
þ
þWhatäoíethodsìookìike?Èere's÷hatôhe÷ithdraw()íethod
þforïurôelleríachineïbjectsíightìookìike:
þ
þscopingïperator ÿÄý¿
þassociatedãlass ÿÄý¿þý³ ýÚÿ Äæunctionîame
þreturnôype ÿÄý¿þ ý³þý³ ý³þõý£ ýÚÿÄárgument
þ þ þ þ
þdoubleôeller_machine::withdraw(doubleámt)
þ{
þbigbucks=ámt;
þif¨bigbucks¼°.0)û
þprintf("Sorry,Ãharlie,ùou'reïverdrawn!\n");
þbigbucks=±0.0;¯/ãhargeæorïverdraft
þ}
þreturnâigbucks;
þ}
þ
þHow'sôhis ý ( 0 - / ( 1ÿýÙ\ met03b þ Scopingïfíethods
þ
þMethodsáren'tñuiteìikeïrdinaryæunctions.Ôheyìookðretty
þmuchôheóame,âutôheyèaveópecialáccessôoôheïther
þmembersïfánïbject.Ópecifically,ôheyãanáccessôhem÷ithout
þusingôhe§.'îotationùouõsuallyõse÷ithïbjectíembers:
þÿý¹
þdoubleôeller_machine::withdraw(doubleámt)
þ{
þnoteáccess ÿÄý¿
þtoäataïfþ
þobjectþbigbucks=ámt;
þif¨bigbucks¼°.0)û
þprintf("Sorry,Ãharlie,ùou'reïverdrawn!\n");
þbigbucks=±0.0;¯/ãhargeæorïverdraft
þ}
þreturnâigbucks;
þ}
þ
þCallingí ý ) 2 . 0 ( 1ÿýú^ met03a
þ Scopingïfíethods
þ
þMethodsáren'tñuiteìikeïrdinaryæunctions.Ôheyìookðretty
þmuchôheóame,âutôheyèaveópecialáccessôoôheïther
þmembersïfánïbject.Ópecifically,ôheyãanáccessôhem÷ithout
þusingôhe§.'îotationùouõsuallyõse÷ithïbjectíembers:ýÓ
þ
þdoubleôeller_machine::deposit(doubleámt)
þ{
þnoteáccess ÿÄý¿
þtoäataïfþ
þobjectþ
bigbucks«=ámt;
þ}
þ
þCalli ý ) 2 . 0 ( 1ÿý` ²met04 þ Callingíethods
þ
þBecauseôheyâelongôoïbjects,ùouãan'tãallíethodsäirectly.
þInstead,ùouãallôhemâyóendingáíessageôoôheïbject:
þ
þObject ÿÄý¿þýÚÿÄÍethod
þ þ
þmy_bank.deposit(paycheck);
þ þ þ
þ familiaräot ÿÄýÙþýÀÿÄýÙ
þ notat¸ýð ionæorþ
ýÀÿÄÍessage
þ accessingótructure
þ members
þ
þcash½íy_bank.withdraw(100.00);
þ þ þ
þý³þýÀÿÄýÙ
þýÀÿÄÒeturnöalueþýÀÿÄÍessage
þ
þTalkingôoÏbjects®..þTourÇuid4ý ( ) / 3 # 3 ( 1 6 8 ÿýb ·msg01 þ
Here'sôalkingôoùa-ôhatés,ÍessageÐassing
þ
þOOPðeopleèaveáäifferentîameæorãallingæunctions.Ét's
þnow¢messageðassing." ×hat'sôheäifference? ×ell,ôheôerm
þmessageðassingãonnotesáíoreåventäriven,íodularîetwork.
þObjectsïperateénðarallel,áÿýc ndôheyãommunicateâackánd
þforth.
þýÚÿÄý¿þ ýÚÿ Äý¿
þý³ÓhakyÓavings ý³¼ÿÄ> ý³ÂrokeÂank ý³
þýÀÿÄýÙþý³þýÀÿ ÄýÙ
þ%ý³
þýÚÿÄý¿þý³þýÚÿÄý¿
þý³ÃoldÃashÉnc ý³¼ÿÄ> ý³ÃounterfeitÂank ý³
þýÀÿÄýÙþ ý³þofÁZþý³
þ*ýÀÿÄýÙ
þ
þWell,áctually,énÃ++,ïb¹ý jectsäon'tïperateénðarallel.
þWe'reótill÷ithóequentialíachines,äarnétányway!Åven
þso,ôheôermíessageðassingéndicatesôheópiritïfïbjects
þaséndependentìittleâlackâoxes.
þGettingôh ý + 4 0 2 # ,ÿýee 7msg02 þGettingôheÍessageénÃ++
×hatésíessageðassingòeallyìikeénÃ++?×ell,ét'sêustæunction
ãalling.Âutîotêustôoányæunctions,òather,æunctionsôhat
âelongôoïbjects.Ôheseáreãalledíethods.Ôheíethodsáreôhe
íessageóelectors,ôheárgumentsáreôheíessÿýef ageãontents.
þTypeïfïbject ÿÄý¿þ
ýÚÿÄÏbject
þ þ
þteller_machineíy_bank;
þdoubleðaycheck½±00.0; ÿÄðlainïle'Ãöars
þdoubleðarty_money;
þObject ÿÄý¿þýÚÿÄÍethod¨messageóelector)
þ þ
þmy_bank.deposit(paycheck);þýÚÿÄíessageãont;ý ents
þ0
þparty_money½íy_bank.withdraw(500.00);
þ
þ ý % ) + # ,ÿýÂg Gclass01
þ IntroducingÃlasses
þ
þ
þ Classesáreátôheèeartïfïbject-orientedðrogramming
þ inÃ++.Âut÷aitáíinute,÷hyáren'tïbjectsôheãentral
þ feature?Ôheôruthés,÷ithoutãlasses,ùou÷ouldn'tèave
þ objects,âecauseãlassesáre÷hatïbjectsáreâuiltærom.
þ
þ
Dý8 ×határeãlasses?
þ
Ãlassesásïbjectôemplates
þ
Ãomponentsïfáãl4ý ( 6 )
#
8 # % ÿý þ Whatáreãlasses?
þ
þ ClassesáreåxtensionsôoÃótructures.Ôheyádd:
þ
þÄataèiding
þÍethods
þÉnheritance
þ
þ Hereésáóampleãlass:
þ
þclassãircleûþ <ÿÄãlassäeclaration
þdoubleòadius;þ<ÿÄðrivateíember
þpublic:þ<ÿÄðublicíembersæopýS llow
þvoidénit(doubleò);¼ÿÄáíethod
þdoubleárea(void); ¼ÿÄánotheríethod
þ};
þ
þRelationshipôoÓtructu>ý 2 9 - > , 7 2 4 & (ÿýìj Áclass02b þClassesösÓtructures
ÉnÃ++,ùouèaveôheïldÃótructures,îewÃótructures,ánd
ãlasses.Ôheòelationshipâetweenôheôhreeésçivenâelow:
Ãótructureþ C++ótructureþC++ãlass
ôypedefótructûþstructòectûþclassòectû
þint÷d,èt;þ int÷d,èt;þÿýìk public:
}òect;þ
};þint÷d,èt;
þ*};
Îoteôhat,õnlikeÃótructures,Ã++ótructuresáreâona-fide
õser-definedôypes,óoùouäon'tîeedôoõseôypedef.Álso,îote
èowáãlass÷ithállðublicíembersándîoæunctionsésêust
ìikeôheÃótructureïfïld.Ã++ótructuresándãlaµýg ssesçoâeyond
Ãótructuresénôhatôheyãanèaveæunctionsôoo.
Äon'tæorgetôhatùouãanótillèaveÃótructuresénùourãode,ôhat
és,ùouãanõseôypedeféfùou÷ant.Ã++ésõpwardãompatible÷ithà ý + 8 2 4 ÿýÃm .class03 þComponentsïfáãlass
þ
þInçeneral,ãlassesãanèaveðublic,ðrivate,ándðrotected
þmembers.Ôheseíembersãanâeïtherïbjectsæromïtherãlasses,
þandíethods¨i.e.æunctions):
þ
þýÚÿ
ÄÃlassëeyword
þý³þýÚÿÄÃlassîame
þ þ
þclassóhapeû
þprivate:þÿýÃn
//Ðrivateëeyword
þdataíember ÿÄ énténit_flag; ¯/Ðrivateíember
þprotected:þ//Ðrotectedëeyword
þdataíember ÿÄ äoubleøo,ùo; ¯/Ðrotectedíembers
þpublic:þ //Ðublicëeyword
þ method ÿÄ- énit(doubleø,äoubleù); ¯/ðublicíember
þ method ÿÄ- äo6ý ubleárea(void);þ //ðublicíember
þ};
þ
þClassíeRý F .
4
;
. 6 < . 3 : - $ 5 , . 1ÿýMp encap01
þDataÈiding ¨orÄataÅncapsulationásôheôechiesãallét)
Ôheæancyôermäataåncapsulationêustíeansôoåncloseándèide
äata÷ithináãlass.Ôoèideäataénáãlassíeansôhatïnlyíembers
ïfôhatãlassãanáccessét.
Ã++ðrovidesôhreeìevelsïfäataèidiný§ g:
þÐublic
þÐrivate
þÐrotected
Énáddition,ùouãanèaveæriendæunctionsôoáccess
ðrivateíembersïfãlasses.
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þPo ý ( \ - / ÿý]© over01 þOverloadingÆunctions
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þToïverloadæunctionsíeansôoçiveôwoïríoreæunctionsôhe
þsameîame:
þ
þdoubleádd(doubleá,äoubleâ)þcharªadd(charªa,ãharªb)
þ{þ"{
þ returná«â;þreturnótrcat(a,â);
þ}þ"}
þ
þdoubleá,â;þcharªs,ªt;
þ
þa½ádd(a,b);þÿý]ª t½ádd(t,ó);
þ
þTheôrickésôoíakeóureátìeastïneïfôheðarametersés
þdifferent,¨byèavingáäifferentôype),ïrâyèavingá
þdifferentîumberïfðarameters.Ôhisésóoôheãompilerãan
þfigureïut÷hichïneôoâindôheãallôo. Ïtherwise,
þyou'llçetáäuplicateæunctionårror.ýS
þ
þMore®..þP4ý ( a _ ' \ , 7
ÿý¨« over02
þAdvantagesôoÆunctionÏverloading
Âeingábleôoïverloadæunctionsèasét'sádvantages,óinceùouãan
õseíeaningfulîamesæorùouræunctions,÷ithoutèavingôoôackïn
ánnoyingðrefixes.Æorénstance,ãontrastôheðreviousãardôoôhis:
Ðrefix ýÄý¿þ Prefix ýÿý¨¬ Äý¿
þ þ$
äoubleäouble_add(doubleá,äoubleâ) ãharªstr_add(charªa,ãharªb)
ûþ&{
þreturná«â;þreturnótrcat(a,â);
}þ&}
Éfùou'reæamiliar÷ithÍicrosoft×indows,ÐresentationÍanager,
Óun×indows,åtc.,ùou'llémmediatelyòecognizeôhisánnoyance.
þ Canïver ýw loadingôheïperatorsôoo®..þ*ý 0 < ^ - ` 2 = ' 2ÿýó overop01 þOverloadingÏperators
þ
þYouãanálsoïverloadôheïperators!Ôhisésäoneâyãreating
þoperatoræunctions.Ôheseæunctionsèaveîamesïfôheæorm
þ"operatorïp,"ándãanâeénvokedâyõsingôheássociatedïperator:
þ
þ FunctionÎameþFeatureÍenuþOOE
þ
ýÚÿÄý¿
ÿýó® þ
þ
þtimeïperator+(timeá,ôimeâ) ÿÄý¿
þ{þ þ,ý³
þ timeã; ýÀÿÄ«ïperatorþ
ý³
þ returnã½á.val«â.val;þ
þ}þ9ý³
þBý³
þtime÷ork_time,âusy_time,çoof_off_time;þý³
þBý³
þ ýÚÿÄãausesæunctionãall
þwork_time½âusy_time«çoof_off_time;
þ
þTheïpera(ý ndôypesäetermine÷hichïperatoræuncti ý ) . 0 0 ;ÿý=° ¶bind01 þ FunctionÂinding
þ
þFunctionâindingíeansôoìinkõpáæunctionãall÷ithôhe
þappropriateæunction.
þ
þ
FunctionÃalls:þFunctionÃode
þ
þ(ýÚÿÄý¿
þ
sit_on_it(); ÿ
Äý¿ ýÚÿÄý³äo_something();þý³
þ!ýÀÿÄý¿ ý³þý³
þ
think_about_it(); ÿÄý¿ ý³ýÀ²ý£ ýÄý³óit_on_it();þý³
þ!ýÀÿÄý³ý¿ ý³þý³
þ
do_something(); ÿ
ÄýÙýÀýÄý³ôhink_about_it(); ý³
þ(ý³þý³
þ(ýÀÿÄýÙ
þThereáreôwoôypesïfâindingénÃ++:
þ
þ
ÓtaticÂinding
þ
Ä ý
b
e 0 ;ÿý² Üstat01 þ StaticÂinding
×ithótaticâinding,ôheæunctionãallésìinkedõp÷ithôheæunction
átãompileôime.ÉnÃ,ôhisésåasy,óinceállôheãompilerèasôo
ésìookæorôheæunction÷ithôheçivenæunctionãallîame.
þ ýÚÿ Äý¿
þ ý³þ
þ ý³ éntãompute_ultimate_answerÞý¿ (intá,éntâ)
þ ý³ û
þ ý³þreturná*4«â;
þ ý³ }
þ ý³ ®ÿ.
þ ý³
þ ý³ ë½ãompute_ultimate_answer(25,±7);
þ ý³þ
þ ýÀÿ
ÄýÙ
Èowever,énÃ++,ét'sáìittleíoreãomplex,âecauseùouãan
èaveæunctionïverloading.
þMore®..þB*ý ^ c % 0 a ' 2ÿý´ stat02 þStaticÂinding÷ithÆunctionÏverloading
þ
þToâindánïverloadedæunction÷itháæunctionãall,ôheãompiler
þmustìookátôheôypesénvolved: ýÚÿÄý¿
þ&ý³þ
þdoubleádd(doubleá,äoubleâ); ý³þintádd(intá,éntâ);
þ{þ ý³þ{þ þ
þ&ý³þ
ýÀÿÄý¿ ý³
þreturÿýµ ná«â;þý³þreturná«â; ý³ ý³
þ}þ ý³þ}þý³ ý³
þ&ý³þý³ ý³
þinté,ê,ë;þý³þý³ ý³
þýÚÿ ÄýÙþý³ ý³
þý³þýÚÿ+ÄýÙ ý³
þý³þý³ ýÚÿ+ÄýÙ
þ þ
þk½ádd(i,ê);
þ
þLikewise,ôhere'sáóomeádditional÷orkénvolvedénâinding
þmethodsïfïbjects.
þ
StaticÂiýÕ nding×ithÍethods®. ý
+ d / : a " -ÿýT¶ östat03 þStaticÂinding÷ithÍethods
þ
þBindingáíessageôoôheáppropriateíethodésóimilar
þtoôheâindingæorïverloadedæunctions,åxceptèere,÷eíust
þfirstçetôheïbject'sãlassándõseétæoríatchingás÷ell:
þ
þýÚÿ Äý¿þ ýÚÿÄý¿
þý³þ þ þý³
þý³ öoidãlock::tþýï ick(intóec) ý³
þý³þ þ ý³
þý³ ûþ
ýÀÿÄý¿þý³
þý³þclock.val«=óec; ý³þý³
þý³ }þý³þý³
þýÀÿÄý¿þý³þý³
þ þý³þý³
þclockâig_ben;þý³þý³
þ þýÚÿ ÄýÙþý³
þ ý³þý³þýÚÿ ÄýÙ
þ þ þ
þbig_ben.tick(25);
þDynamicâinding÷ithÍethodsþBinding*ý 3 ) e . 9 a ' 2ÿý~¸ odyn01 ÿ
þ DynamicÂinding
þ
þ
þDynamicâindingïccurs÷henôheæunctionãallésâoundôoôhe
þfunctionãodeátòun-time. Ùouãançetäynamicâindingây
þusingénheritanceándöirtualíethods.Ùouãanálsoõse
þfunctionðointers;ùou'veðrobablyäoneóoùourselfáôimeïr
þto.lýÿ Èowever,÷ithöirtualíethods,állôhisîastyðointer
þbusinessésèandledâyôheãompiler,îotùou.
þ
þShowíeèow® ý # ( 3 a ' 2ÿý º Òbridge01 þ BridgingôheÇap
þ
þ
þtþo
þ/d\þ ÿ=þ /o\
þpþ===þ===þp
þÿÄ\===þ ===/ÿÄ
þ TheÏldÃountryüþC++þ| ÔheÏbject-Oriented
þ (Traditionalþ\þ/ Ærontier
þ
Programming)þ\þ/
þ ÿ÷
þ Gulfïf
þ Object-Orienta
þ
þOneïfÃ++'síainótrengthsésËý ôhatùouãanìearnôheîew
þfeaturesïfïbject-orientedðrogramming÷ithoutçivingõp
þwhatùouálreadyënow.Énæact,÷e'reîowçoingôoôakeùou
þthrougháìittleåxerciseïfôurningáÃðrograméntoán
þobject-orientedÃ++ðrý
' g !
,ÿýï» "bridge02 þAÄecompressionÁlgorithm
þforÒunÌengthÅncoding
þ
þSupposeùouèadóomeôextôhatésòun-lengthåncodedás
þfollows.Áâyteãontainingá°xffãodeéndicatesôhatôhe
þfollowingôwoâytesãontaináòepeatãountæollowedây
þtheãharacterôoòepeat.Ányïtherâytesárÿýï¼ eðassedótraight
þonôhrough.Æoråxample,
þ
þ ýÚÿÄý¿
þ
aÜxffÜ03âã ÿÄ- ý³Äecomp ý³ ÿÄáâââã
þ ýÀÿÄýÙ
þ
þYouríission,óhouldùouäecideôoácceptét,ésôoôake
þaÃöersionïfôheäecompressionálgorithmándíakeét
þobject-oriented. Äon't÷orry,÷e'llâeèelpingùo ý9 uïut
þeveryótepïfôhe÷aý
h !
,ÿý#¾ ¥bridge03 þTheÄecompressionÁlgorithménÃ
þ
þ Here'sáôypical÷ayùouíightãodeôheäecompression
þ algorithménÃ.Ôhisöersionôakesáãharacterótring
þ ofìengthórclenándðrintsétôoôheócreen.
þ
þ voidäecomp(unsignedãharªs,éntórclen)
þ {
þintã,òcnt;
þ
þwhile¦ý] (srclen--¾°)û
þc½ªs++;
þif¨c½=°xff)û¯*òunìengthäecompressª/
þrcnt½ªs++; 㽪s++;órclen=²;
þwhile(rcnt--)ðutchar(c);
þ}
þelseðutchar(c);
þ}
þ }
þWhat's÷roý
/ i !
,ÿýá¿ Ábridge04 þWhat's÷rong÷ithôhis?
þ
þAlthoughïurálgorithm÷orksæine,ét'sæairlyòestrictive.
þItãanïnlyäecompressäirectlyôoôheócreen.Étèasîoïther
þmodes.Ðlus,èavingôheénner÷hileìoopíeansét'sçoingôo
þdoôheäecompressionállátïnce.Ùouãan'têustäoétïne
þÿýáÀ stepátáôime.Æorénstance,óupposeùou÷antedôoôreatôhe
þdecompressorásáæilter¨inôheópiritïfÕNIX),ándðass
þtheäecompressedôextïneãharacterátáôimeôoáðarser:
þ
þ ýÚÿÄý¿þýÚÿÄý¿
þcompressedôextén ýÄ- ý³Äecomp ý³ ÿÄ ý³ðarser ý³ ÿÄ
þ ý³Æilter ý³þý»ýt ÀÿÄýÙ
þ ýÀÿÄýÙ
þ
þThis÷ouldíakeùouräecompressorñuiteælexibleándòeusable.
þButèowãanùouãhangeïurÃálgorithmôoäoôhis?Ôheánswer
þlies÷ithíakingétáìittleíoreïbject-oriented.
þ
þAìý
1 j !
,ÿý´Â
bridge05 þAÌittleÍoreÏbject-Oriented
þ
þThe÷ayôoíakeïurÃðrogramíoreïbject-orientedésásæollows.
þFirst,ìiftïutôheìocalöariablesôoïuräecomp()æunction,
þandðutôheménáótructureénstead.Ôhisótructure÷illálso
þholdáðointerôoôheótring÷e'reäecompressiÿý´Ã ng,ándôheótring
þlengthás÷ell:
þ
þtypedefótructû
þýÚÿÄéntórclen,ã,òcnt;ÿÄý¿
þýÃÿÄõnsignedãharªp;þý³
þý³ }äecompressor;þ ý³
þý³þ-ý³
þýÀÿ ÄýÂÿÄý¿þý³
þvoidäecomp(unsignedãharªs,éntórclen) ý³
þ{þýÚÿ
-ý¿þý³
þ
int üã,òcnt;ü ÿÄýÙ
þýý Àÿ
-ýÙ
þ
ý
' k !
,ÿýÚÄ ôbridge06 þAÌittleÍoreÏbject-Oriented¨part²)
þ
þThen,ìet'sóplitïuräecomp()æunctionéntoôwoðarts,ánénit-
þializationæunction,ándôhenáæunctionôhat÷henãalled,çives
þusôheîextãharacter,áutomaticallyäecompressingásétçoes.Ïf
þcourse,ôheæunctionèasôoëÿýÚÅ eepôrackïf÷here÷eáreénôhe
þdecompression.Èowäoesétäoôhis?×ell,÷eðassénáðointer
þtoôheótructure÷eêustíade.Ôhisótructureésénitializedây
þourénitializationæunction,ándëeepsôheénformation÷eîeed
þbetweenôheíanyæunctionãalls.
þ
þFirst,ôheénitializatiéýµ onæunction:
þ
þvoidäecompressor_init(decompressorªdc,õnsignedãharªs,éntìen)
þ{
þdc->p½ó;þ /*ðointôoãompressedótringª/
þdc->srclen½ìen;þ/*énitalizeôheénternalìengthª/
þdc->rcnt½°;þ/*ándòesetôheòunìengthãounterª/
þ}
þ
þý
4 l !
,ÿýÛÇ bridge07 þOurÄecompressor-ÆilterÓtyle
×rittenásáãharacterâyãharacteræilter,ïuräecompressorîow
ìooksóomethingìikeôhis:
éntäecompressor_next(decompressorªdc)
û
éf¨dc->rcnt¦&äc->rcnt--¾°)òeturnäc->c;¯*äecompressionª/
éf¨!dc->srclenü|äc->srclenÿýÛÈ --¼=°) òeturn1; ¯*÷e'reôhroughª/
äc->c½ª(dc->p)++;þ/*âumpôoîextãharacterénâufferª/
éf¨dc->c½=°xff)û
þdc->rcnt½¨*(dc->p)++)±;¯*äiscountæirstãhar÷rittenª/
þdc->c ½ª(dc->p)++;þ /*èereésòepeatãharacterþ*/
þdc->srclen=²;
}
òeturnäc->c;
ýÞ }
þ MainÐrogram®.ý
+ m !
,ÿý
Ê Bbridge08 þ Here'sáÓampleÍainÐrogramÕsingÏurÄecompressor
þ
þcharâuff[]½û'a',0xff,3,'b','c'};
þ
þvoidíain()
þ{
þintã;
þdecompressoräc;
þ
þdecompressor_init(&dc,âuff,óizeof(buff));
þwhile¨(c½äecompressor_next(&dc))¡=1)ðutchar(c);
þ}
þ
þNÿý
Ë oteôhatôheíainðrogramäoesîotënowèowôheäecompressor
þworks,étêustðassesárgumentsôoét.Álso,óinceétòunsôhe
þdecompressorïneãharacterátáôime,÷eãouldõseétáíulti-
þtudeïf÷ays.Æorénstance,÷eãouldõseétôo÷riteäirectly
þtoôheócreenìike÷eäoèere,ïr÷eãouldðas8ýë sétôoáótring
þsearchòoutine,ïrôoáðarser®..ùouçetôhý
, n !
,ÿýZÌ bridge09 þMoreÁdvantagesôoánÏbject-orientedótyle
þ
þWithïuräecompressor÷rittenïbject-style,ùouãouldåvenèave
þmoreôhanïneäecompressionçoingïnátïnce.Ôhisésâecause
þweìiftedïutôheénternalöariablesándðutôheménáótructure,
þandîothingótopsõsæromèavÿýZÍ ingíoreôhanïneãopyïfét:
þ
þcharâuff1[]={'a',0xff,3,'b','c'},âuff2[]={'z','y',0xff,4,'x'};
þvoidíain()
þ{
þintã1,ã2;
þdecompressoräc1,äc2;¯/îote÷eèaveÔWOïfôhem
þ
þdecompressor_init(&dc1,âuff1,óizeof(buff1));
þdecompressor_init(&dc2,âuff2,óizeý! of(buff2));
þdoû
þ if¨(c1½äecompressor_next(&dc1))¡=1)ðutchar(c1);
þ if¨(c2½äecompressor_next(&dc2))¡=1)ðutchar(c2);
þ}÷hile¨c1¡=1ü|ã2¡=1);
þ}
þý
0 o !
,ÿýÏ ÿbridge10
þ It'sÅasierénÃ++
þ
þWe'veîowíadeïurÃãodeæairlyïbject-oriented.Èowever,ço
þbackándìookátïuräecompressor_next()æunction,ôhenãome
þbackèere.Âack®.. Îoticeèow÷eèaveáìotïfðointer
þdereferences.Æoråxample:
þ
þdc->c½ª(dc->p)++;þ/*âumpôoúý4! îextãharacterénâufferª/
þif¨dc->c½=°xff)û
þ dc->rcnt½¨*(dc->p)++)±;¯*äiscountæirstãhar÷rittenª/
þ dc->c ½ª(dc->p)++;þ /*èereésòepeatãharacterþ*/
þ dc->srclen=²;
þ}
þ
þThat'sðrettyõglyãoding.Ãan÷eémproveét?Ùes÷eãan,ây
þusingÃ++!
þ
þOnôo ý l 0 p ' 2ÿý+Ñ 0bridge11
þOnôoôheÃ++Ærontier
ÔoôurnïurÃãodeéntoÃ++,ôheæirstôhingésôoôurnïur
äecompressorótructureéntoáãlass:
ôypedefótructûþ classäecompressorû
þintórclen,ã,òcnt;þintórclen,ã,òcnt;
þunsignedãharªp; ½==>> õnsignedãharªp;
}äecompÿý+Ò ressor;þ
public:
þ decompressor(unsignedãharªs,éntìen);
þ intîext(void);
þ };
Îoteèowïurãlassãontainsôwoæunctionsás÷ellásïur
ótructureäata.Ìet'sôakeáãloserìookátôheæunctions.
Ôheæirstæunctionésënownásáãonstructor,ándésôhe
åquivalentïfïuräe,ýQ! compressor_init()æunction.
þTheÄeco ý ! % 5 3 q ' 2ÿýyÓ 1bridge12 þTheÄecompressorÃonstructor
þ
þHere'sôheÃöersionïfïurénitializationòoutine:
þ
þvoidäecompressor_init(decompressorªdc,õnsignedãharªs,éntìen)
þ{
þdc->p½ó; äc->srclen½ìen; äc->rcnt½°;
þ}
þ
þHere'sôheÃ++öersion,õsingáãonstructor:
þ
ÿýyÔ þdecompressor::decompressor(unsignedãharªs,éntìen)
þ{
þp½ó;órclen½ìen;òcnt½°;
þ}
þ
þNoteèow÷e'reáccessingôheótructureöariablesð,órclen,ánd
þrcntäirectly,÷ithoutäeferencingányðointers.ÉnÃ++,æunctions
þbelongingôoáãlassãanäoôhis.Ét'såveníoreära%ýs! matic÷ithôhe
þdecompressorîext( ý $ . # - r ' 2ÿýÀÕ bridge13 þTheäecompressorîext()æunction.
þ
þintäecompressor::next(void)
þ{
þif¨rcnt¦&òcnt--¾°)òeturnã; ¯/äecompressingòunìength
þif¨!srclenü|órclen--¼=°) òeturn1; ¯/÷e'reátånd
þ
þc½ªp++;þ //âumpôoîextãharacterénâuffer
þif¨c½=°xff)û
þ
rcntÿýÀÖ ½ªp++±;¯/äiscountæirstãhar÷ritten
þ
c ½ªp++;þ//èereésòepeatãharacter
þ
srclen=²;
þ}
þreturnã;
þ}
þ
þCompareôhis÷ithïurÃöersionâyÐressingíe.Ôhen
þcomeâackèere.×hichöersion÷ouldùouòatherìookát?ÔheÃ++
þversionìooksáìotóimplerándãleaner,äoesn'tý! ét?
þ
þNowìet'sóee ý ( 2 l 5 s ' 2ÿýû× bridge14 þAÃ++ÐrogramÕsingïurÄecompressorÃlass.
þ
þunsignedãharâuff[]½û'a',0xff,3,'b','c'};
þ
þvoidíain()
þ{þýÚÿÄÄeclaringáäecompressorïbject,
þý³ ándåvenénitializingétátôhe
þý³ óameôime.
þintã;þ
þdecompressoräc(buff,óizeof(buff));
ÿýûØ þ
þwhile¨(c½äc.next())¡=1)ðutchar(c);
þ}þ
þýÀÿÄ×e'reðassingáíessageôoôheïbject
þ
þViola!Ùou'veêustäoneùouræirstãonversionæromÃôoÃ++.
þOfãourse,ùouäidn'tèaveôoãonvertùourïriginalÃðrogram,
þit÷ouldèaveòanêustæineénÃ++,âutét÷ouldn'tèaveâeen
ý¼! þasïbject-oriented4ý ( ! " - #
.
3 , t
ÿýIÚ Ðbridge15 þ AltogetherÎow
þ
þLet'sðutïurÃ++äecompressorðrogramáltogetherîow.Èere
þisôheãompleteðrogram¨justðageäownôoóeeíoreïfét):
þ
þ 001:£include¼stdio.h>
þ 002:
þ 003:ãlassäecompressorû
þ 004: éntórclen,ã,òcnt;
þ 005: õnsignedãharªp;
þ 006:¼ýß! ðublic:
þ 007: äecompressor(unsignedãharªs,éntìen);
þ 008: éntîext(void);
þ 009: };
þ 010:
þ 011:äecompressor::decompressor(unsignedãharªs,éntìen)
þ 012:û
þ 013: ð½ó;órclen½ìen;òcný
+ u 'ÿý Ü ¬bridge16
þAltogetherÎow¨part²)
þ
þ015:éntäecompressor::next(void)
þ016:û
þ017: éf¨rcnt¦&òcnt--¾°)òeturnã;þ //äecompression
þ018: éf¨!srclenü|órclen--¼=°) òeturn1; ¯/÷e'reôhrough
þ019:
þ020: 㽪p++;þ //âumpôoîextãharacterénâuffer
þ021ý " : éf¨c½=°xff)û
þ022:þrcnt½ªp++±;¯/äiscountæirstãhar÷ritten
þ023:þc ½ªp++;þ//èereésòepeatãharacter
þ024:þsrclen=²;
þ025: }
þ026: òeturnã;ý
v 'ñý3" þ bridge17 ÿ
þAltogetherÎow¨part³)
þ
þ
028:õnsignedãharâuff[]½û'a',0xff,3,'b','c'};
þ
029:
þ
030:öoidíain()
þ
031:û
þ
032: éntã;
þ
033: äecompressoräc(buff,óizeof(buff));
þ
034:
þ
035: ÷hile¨(c½äc.next())¡=1)ðutchar(c);
þ
036: }
ý
, 'ÿýÚÞ ÿref01 þ ReferenceÖariables
þ
þReferenceöariablesáreáliasesæorïtheröariables.Ôheyâehave
þlikeðointersôhatáreáutomaticallyäereferenced÷henõsed.Ôhey
þareäeclared÷ithôhe§&'ïperator,ásén:
þ
þinté½´2;
þint¦k½é;þ//ëòeferences,ïráliases,é
þprintf(ûýR" "%d\n",ë);¯/ëäereferencedáutomatically,ðrints´2
þk½µ5;þ //óetsâothëÁNDéôoµ5
þ
þ
Here'sèowôheótatementsáboveôranslateôoÃ:
þ
þC++þC
þ
þinté½´2;þinté½´2;
þintªk½¦i;þ
int¦k½é;
þprintf("%d\n",ªk);þprintf("%d\n",ë);
þ*k½µ5;þk½µ5;
þ
þMore ý x $ /
(ÿý÷à oref02 þUsingÒeferenceÖariablesásÁrguments
þ
þReferenceöariablesáreõsefulásárgumentsôoæunctions,
þandðrovideáîew÷ayôoäoðass-by-reference.Æoråxample,
þ
þ structòectû
þ
int÷d,èt;
þ };þ ýÚÿÄðassâyòeference
þ
þ intárea(rect¦r)
þ {
þreturnò.wdªòwýn" .ht;
þ }þ
þýÀÿÄ-§.',îot§->'¡
þ
þýÚÿÄäon'tîeedôoõse§&'èere
þ rectò;þ
þ intë½área(r);
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þMore®..þFeature ý y % 0
(ÿýâ òref03
þ TranslationïfÒeferenceÖariablesÕsedásÁrguments
þCþC++
þtypedefótructûþ
structòectû
þint÷d,èt;þint÷d,èt;
þ}òect;þ};þ ýÚÿÄ-ðassâyòeference
þ,
þintárea(rectªr)þ intárea(rect¦r)
þ{þ{
þreturnò->wd*r->ht;þreturnò.wdªò.ht;
þ}þ}þÿý
þ(ýÀÿÄ-§.',îot§->'¡
þrectò;þrectò;
þintë½área(&r);þ intë½área(r);
Îoteèowôheótructureíembersáreäereferencedõsingôhe§.'îotation,
òatherôhan÷ith§->'.Ðascaláfficionados÷illòecognizeôhatòeference
árgumentsáreánalogousôoÖARðarameters. ÆeatureÍenu ý~" þ
þ Fý
- 8 (ÿý³ä def01 þ DefaultÁrguments
þ
þC++állowsùouôoèaveäefaultárgumentsénæunctionãalls.
þYouäoétâyäefiningánássignmentÉNÔHEÐARAMETERÌIST
þITSELF.Èere'sánåxample:
þ
þ
#defineÒED °x04
þ
#defineÂLUE°x01
þ
þdefaultsôoôheãoloròed--|
þ-v
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voidóet_pixel(iýã ntø,éntù,éntã½ÒED)
þ
{
þ ...
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}
þ
þ
set_pixel(100,100,BLUE); ¯/ïverridesäefaultãolor
þ
set_pixel(200,300);þ//õsesäefaultãolorïfÒED
ý
) (ÿýVæ tproto01
þFunctionÐrototyping
þ
þFunctionðrototypesáreæorwardäeclarationsôhatállowôhe
þcompilerôoäoôypeãheckingïnæunctionãalls.Èere'sán
þexample:
þ
þ voidðrt(charªs,éntìen); ¯/æunctionðrototype
þ
þ i½±5;
þ
þ prtchar(&i,¢hello"); ¯/ãausesãoký" mpilerårror!
þ
þActually,íostîewÃãompilersèaveæunctionðrototypingîow,
þasét'sðartïfôheîewÁNSIÃótandý
) (ÿýÙç Ïnew01
þNew¦ÄeleteÏperators
Ã++èasáîewóetïfíemoryállocationæunctionsôhatãanâeõsed
æoräynamicíemory-îewándäelete.Ôheseæunctionsáreáctually
õsedásïperators:
þýÚÿÄîoteïperator
þ
þdoubleªd½îewäouble;
þdeleteä;
þ
þýÀÿÄîoteïperÊýµ" ator
Îewésåspeciallyöaluableâecauseétäoesôypeãheckingôoóeeèow
íuchíemoryôoállocate.Ùouäon'tèaveôoôellét.Æorénstance,ét
ënowsáboveôoállocateåightâytesæorôheäoubleðointer.
þTranslationôo ý $ } + 6
(ÿýÅé ¯new02
þ TranslatingîewándäeleteôoÃ'síalloc()ándæree()
à íustçiveóize ýÄý¿þC++
þ
äoubleªd½íalloc(8);þ
doubleªd½îewäouble;
æree(d);þdeleteä;
ãharªq½íalloc(sizeof(int)*10); ãharªq½îewént[10];
æree(q);þdelete[10]ñ;
Îotïnlyáreîew¦äel±ýÒ" eteóafer,ôheyãanálsoãauseãonstructors
ándäestructorsôoâeáutomaticallyãalled.Ôheseállowùouôoäo
énitializationándãleanupátôheóameôimeùouállocateándäeallocate
íemory.
þ F*ý 7 B #
( ) &ÿý¢ë østream01 þ StreamÉ/O
þ
þC++èasá÷holeîew÷ayïfäoingÉ/O,õsingôheïperators§>>'
þand§<<'.Âelowésánåxample,ándét'sôranslationôoÃ:
þ
þCþ"C++
þ
þ#include¼stdio.h>þ#include¼stream.h>
þvoidíain()þvoidíain()
þ{þ"{
þintë;þ intë;
þprintf("Enterîum:ôýè" ¢);þ
cout¼<¢Enterîum:¢;
þscanf("%d",¦k);þcin¾>ë;
þprintf("Numberés:¥d\n",ë);þcout¼<¢Numberés:¢¼<ë;
þ}þ"}
þ
þWithÃ++,ùouãanïverloadôhe§>>'ánd§<<'ïperatorsándðrovide
þyourïwnòoutinesôoénputándïutputùourïwnïbjects.
þ
þRollùourïwnÉ/O ý % + 6 'ÿý¸í ïstream02 þ RollùourïwnÉ/O
C++èasôwoãlasseséstreamándïstream÷hicháreõsedôoíakeénputánd
outputïbjectsærom.Ùouãanôhen÷riteùourïwnótreamïperatoræunctions:
ótructãlockû
þintèr,íin,óec;
þclock(intè,éntí,éntó)ûèr½è;íin½í;óec½ó; }
};
þýÚÿ
ÄýÂÿÄýÿý ÂÿÄîoteïstreamïbjectsánd§<<'ïperator
þ þ
þ
ïstream¦operator<<(ostream¦strm,ãlock¦c)
û
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ãlockã(12,31,55);
ãout¼<ã;
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# . ' 2ÿýÏï ôinline01 þ InlineÆunctions
þ
þTheseáreæunctionsôhat,óimilarôoíacros,áreénserted
þinline÷hereverãalled.Ôhisóavesôheïverheadïfáæunction
þcall.Âelowésánåxample:
þ
þ
inlineäoubleôaxem(doubleø)
þ
{
þ returnø*0.50;
þ
}
þ
þ
net½ôaxem(gross);þ Featurëý# eÍenu
þ
þIt'sásôhoughùouóaid
þ
þ
net½çrossª°.50;
þ
þNoteôhatõnlikeíacros,énlineæunctionsèaveåxactlyôhe
þsameóemanticsôhatòegularæunctionsäo.Énðarticular,
þtheyäon'tóufferæromôheótrangeócopingðroblemsùou
þcançet÷ithíacros,áý
) 4 ' 2ÿýÒñ ãvirt01
þ VirtualÍethods
þ
þVirtualíethodsáreáópecialôypeïfíethod.Îo,ôheyáren't
þstoredénöirtualíemory,ïránythingìikeôhat.Állôhat
þhappensésôhat,õnlikeîormalíethods,ãallsôoöirtual
þmethodsáreâoundátòun-time,îotátãompile-time.Ôhis
þdynamicâindÿýÒò ing,ïrìateâindingásét'sóometimesãalled,
þoccursâyõsingæunctionðointers.
þ
þEveryãlassïfïbject÷ithöirtualæunctionsèas÷hatésënown
þasáöirtualíethodôable.Énôhisôableáreðointersôoáll
þtheöirtualíethodsïfôheãlass.Åachïbjectïfôheãlass
þhasáðointerôoôØý%# hisôable,óo÷henáöirtualíethodés
þcalled,ôhisðointerésôraversed,ôheáppropriateôableåntry
þisïbtained,ándôhenôheæunctionðointerésôraversedôoôhe
þactualíethod.Ôhus,öirtualíethodsénvolveôwoìevels
þoféndirection. ý % 0 a 'ÿýÌô virt02
þSampleÃlass÷ithÖirtualÍethods
þ
þGivenôheãlassóhape÷ithôwoöirtualíethods,
þ
þclassóhapeû
þpublic:
þdoubleøo,ùo;
þshape(doubleø,äoubleù);¯/ãonstructorôoénitializeóhape
þvirtualäoubleárea(void);¯/æctnôoãomputeóurfaceárea
þvirtualäzýN# raw(void);þ//æctnôoärawóhape
þ};
þ
þtheîextãardóhowsèowôheöirtualíethodsôableìookæor
þanïbjectïfôhisãlass.
þ
þ ý $ / a 'ÿýhö virt03 þAÖirtualÍethodÔable
þ
þShapeÏbject'sþ VirtualÍethodþActual
þ DataþTableþ
Function
þ
þýÚÿ
Äý¿ ýÚÿÄ ýÚÿ Äý¿
þý³ øo,ùo ý³ ý³þý³¨*area)()ÿÄ óhape::area()
þýÃÿ
Äý´ ý³þýÃÿ Äý´
þý³ öptrÿÄýÙþý³¨*draw)()ÿÄ óhape::draw()ûýn#
þýÀÿ
ÄýÙþ ýÀÿ ÄýÙ
þ
þSoôoãalláóhapeïbjectsäraw()æunction,ãodeóomething
þsimilarôoôheæollowingésõsed:
þ
þ my_shape.draw() ÿÄ ª(my_shape.vptr[1]);
þ
þThatés,åachöirtualíethodéséndexedïutïfôheôable.Ôhis
þindexingésãomputedátãompileôime. ý $ / a 'ÿý ø Ëvirt04
þ!So×hat?
þ
þByîow,ùou'reôhinking¢So÷hat?"×hat'sóoçreatáboutôhis
þelaborateæunctionðointerócheme?×ell,óuppose÷eõsed
þinheritanceándäerivedáîewãlassæromóhape:
þ
þclassãircleºðublicóhapeû
þpublic:
þdoubleòadius;
þcircle(doubleø,äoubÁý# leù,äoubleò);
þdoubleárea(void);¯/ïverridesóhape::area()
þdraw(void);þ//ïverridesäraw::area()
þ};
þ
þTheîextãardóhowsèowôheöirtualíethodôable÷ouldìookîow:
þ
þ
Virtualíethodôableæorã ý
- 1 < a 'ÿýhú @virt05
þVirtualÍethodÔableæorÃircles
þ
þCircleÏbject'sþ VirtualÍethodþActual
þDataþTableþ
Function
þ
þýÚÿ
Äý¿ ýÚÿÄ ýÚÿ Äý¿
þý³ øo,ùo ý³ ý³þý³¨*area)()ÿÄ ãircle::area()
þý³ òadius ý³ ý³þýÃÿ Äý´
þýÃÿ
Äý´ ý³þý³¨*draw)()ÿÿýhû Ä ãircle::draw();
þý³ öptrÿÄýÙþýÀÿ ÄýÙ
þýÀÿ
ÄýÙ
þ
þTheãircleãlassèasáãopyïfôheöirtualíethodôableærom
þclassóhape,ándåachöirtualæunctionïverriddenâyôheãircle
þclass¨inôhisãaseállïfôhem)ãauseôheãorrespondingåntries
þinôheôableôoâeíodifiedôo7ý¶# ðointôoôheãircle'söersionïf
þtheæunctions.
þ
þS ý $ ) 4 a 'ÿýÁü évirt06 þAÒeasonæorÔhisÍadness
þ
þThereòeallyésáòeasonæorôhisíadness.Étállowsõsôoõseá
þpointerôoánïbject,òatherôhanôheïbjectétself,ándótillâe
þguaranteedôhatôheòightöirtualíethod÷illâeãalled,âecause
þaðointerôoétésótored÷ithôheïbject.ÆoråxamplÿýÁý e:
þ
þshapeªp;þ //äeclareçenericóhapeðointer
þshapeó(0,0);þ//ándáçenericóhape
þcircleã(10,10,50);¯/ándáãircleóhape
þ
þp½¦s;þ //ðointôoóhape
þp->draw();þ//ãausesóhape::area()ôoâeãalled
þp½¦c;þ //ðointôoãircleÍoreáboutôhis®..
þp->draw();þ//àýÝ# ãausesóhape::circle()ôoâeãalled
þ
þThus,÷ithöirtualíethods,÷eãanèaveïuróhapeðointerðerform
þdifferentâehaviors,äependingïn÷hatëindïfóhapeétðoints
þto.Ôhisés÷hatðolymorphismésállábout!
þ
þOkay,Ïkay,Éâelieveùou,âutè ý ,
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D 'ÿýÃÿ virt07 þDeclaringÖirtualÍethods
þ
þActually,ùou'veálreadyóeenèowôoäoôhis,âut,èereés
þtheóhapeãlasságain:
þ
þclassóhapeû
þpublic:
þdoubleøo,ùo;
þshape(doubleø,äoubleù);¯/ãonstructorôoénitializeóhape
þvirtualäoubleárea(void);¯/æctnôoãomputeÿýÃ óurfaceárea
þvirtualäraw(void);þ//æctnôoärawóhape
þ};
þ ýÀÿÄÖirtualëeyword
þ
þVirtualæunctionsáreäeclaredõsingôheöirtualëeyword.Îote
þthatôhisíustâeäoneénôheâaseãlass,¨likeóhapeèere),âut
þitäoesn'tèaveôoâeenénôheäerivedãlasses.Ïnceöirtual,
ý$ þalwaysöirtua ý % a * , 'ÿýø oneway01
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þYouíightèaveîoticedénïneïfôheãards¨Thisïne®..)
þthatáâaseãlassðointer,óuchásóhapeªp,ãanðointîotïnly
þtoáóhapeïbject,âutálsoôoáãircleïbject.Ôhisésäone
þWITHOUTÔYPEÃASTING.Áctually,ùouãanðointáâaseãlassðoÿýø inter
þtoányäerivedãlassïbject.Æorénstance,óhapeªpãouldðointôo
þrect,ïrâox3d,ïrãylinder,ándïnándïn.Ôhus,ôhere'sáìot
þofðowerðackedénôhatðointer.
þ
þHowever,ôheãonverseésîotôrue.Æorénstance,áãircleðointer
þcannotðointôoáçenericóhapeïbject.×hy?Âeý($ causeãircles
þhaveáòadius,óhapesäon't.Ôhuséfùouôriedôoíakeáóhape
þactìikeáãircle,ándáccessét'sòadius,ôhings÷ouldòeally
þgetæouledõp!
þ
þBackôo ý 0 ; 5 'ÿý² Dfriend01
þ FriendsïfÃlasses
þ
þClassesãanèaveæriends.Ôheseáreæunctionsôhat,álthough
þtheyáreîotðartïfáãlass,ãanèaveáccessôoôheðrivate
þpartsïfôheãlass¨noäirtyíindsèereðlease!).Æorénstance,
þtakeïurôeller_machineãlass,÷ithðrivateíemberâig_buckÿý² s.
þWeãanáddá¢friendly"ÉRSôaxæunctionôoét:
þ
þ classôeller_machineû
þ private:þ//ðrivateëeyword
þ doubleâig_bucks;þ
//ðrivateíember
þ public:þ//ótartsðublicóection
þ voidäeposit(doubleámt); ¯/ðublicíember
þ double÷ithdraw(void);þ//ðublicíember
þLýN$ friendöoidérs(void);þ//¢friendly"æunction
þ };
þ
þMore®.. ÄataÈidin*ý ) 9 , 3 &ÿý* lfriend02
þAÆriendlyÉRSæunction
þ
þ
þ voidérs(void)
þ {
þ big_bucks=âig_bucksª°.10;¯/ôake±0%ïffôheôop
þ }
þ
þNoteôhatálthough÷eäeclaredérs()énsideôheãlass,étés
þnotáãlassíethod!Ôhisésäueôoôheæriendëeywordôhat
þwasõsed.Âutåvenôhoughét'sîotjýd$ áíethod,étãanótillòake
þoff±0%ïfïuróavingsæromïurèiddenâig_bucksótorage.
þ(Someæriend!)
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Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!
This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.
But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/