ThinkinginC++annotatedsolutionguidecharpter5.docx
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ThinkinginC++annotatedsolutionguidecharpter5
Chapter5
5-1
Createaclasswithpublic,private,andprotecteddatamembersandfunctionmembers.Createanobjectofthisclassandseewhatkindofcompilermessagesyougetwhenyoutrytoaccessalltheclassmembers.
（Lefttothereader）
5-2
WriteastructcalledLibthatcontainsthreestringobjectsa,b,andc.Inmain（）createaLibobjectcalledxandassigntox.a,x.b,andx.c.Printoutthevalues.Nowreplacea,b,andcwithanarrayofstrings[3].Showthatyourcodeinmain（）breaksasaresultofthechange.NowcreateaclasscalledLibc,withprivatestringobjectsa,b,andc,andmemberfunctionsseta（）,geta（）,setb（）,getb（）,setc（）,andgetc（）tosetandgetthevalues.Writemain（）asbefore.Nowchangetheprivatestringobjectsa,b,andctoaprivatearrayofstrings[3].Showthatthecodeinmain（）doesnotbreakasaresultofthechange.
（Lefttothereader）
5-3
Createaclassandaglobalfriendfunctionthatmanipulatestheprivatedataintheclass.
（Lefttothereader）
5-4
Writetwoclasses,eachofwhichhasamemberfunctionthattakesapointertoanobjectoftheotherclass.Createinstancesofbothobjectsinmain（）andcalltheaforementionedmemberfunctionineachclass.
Solution:
//:
S05:
PointToMeAndYou.cpp
#include
usingnamespacestd;
classYou;//Forwarddeclaration
classMe{
public:
voidProcessYou（You*p）{
cout<<"ProcessingYouat"<}
};
classYou{
public:
voidProcessMe（Me*p）{
cout<<"ProcessingMeat"<}
};
intmain（）{
Meme;
Youyou;
me.ProcessYou（&you）;
you.ProcessMe（&me）;
}
/*Output:
ProcessingYouat0065FDF4
ProcessingMeat0065FDFC
*/
///:
~
Whentwoclassesrefertoeachother,itisnecessarytoforward-declareatleastoneofthem,asIdidabove.Youmustonlyusepointers,ofcourse,oryou’lltrulyfindyourselfinachicken-and-eggfix.FYI:
whenclasseshavearelationship,forexample,andEmployee“has-a”Manager,itiscommontoreflectthisrelationshipbyactuallystoringapointertotheManagerobjectasamemberintheEmployeeobject,soyoudon’thavetoexplicitlypasspointersasargumentstomemberfunctionslikeIdidhere.
5-5
Createthreeclasses.Thefirstclasscontainsprivatedata,andgrantsfriendshiptotheentiresecondclassandtoamemberfunctionofthethirdclass.Inmain（）,demonstratethatalloftheseworkcorrectly.
Solution:
//:
S05:
MyFriends.cpp
#include
usingnamespacestd;
classHasStuff;//MustprecedeGoodFrienddefinition
classGoodFriend{//MustprecedeHasStuffdefinition
public:
voidhasAccess（HasStuff*p）;
voidhasNoAccess（HasStuff*p）{
cout<<"Cannotaccess"<}
};
classHasStuff{
private:
intx;
friendclassBestFriend;
friendvoidGoodFriend:
:
hasAccess（HasStuff*）;
};
//MustfollowHasStuffdefinition:
voidGoodFriend:
:
hasAccess（HasStuff*p）{
cout<<"FromGoodFriend:
:
hasAccess:
"<x<}
//AllmethodsofBestFriendhaveaccesstoHasStuff:
:
x
//ThismustalsofollowtheHasStuffdefinition:
classBestFriend{
public:
voidinitFriend（HasStuff*p）{
p->x=5;
}
voidqueryFriend（HasStuff*p）{
cout<<"FromBestFriend:
"<x<}
};
intmain（）{
HasStuffh;
BestFriendb;
b.initFriend（&h）;
b.queryFriend（&h）;
GoodFriendg;
g.hasAccess（&h）;
g.hasNoAccess（&h）;
}
/*Output:
FromBestFriend:
5
FromGoodFriend:
:
hasAccess:
5
Cannotaccess0065FE00
*/
///:
~
Thisisanotherexerciseinforwarddeclarations.ThedefinitionofGoodFriendrequirestheexistenceofclassHasStuff,butIcannotincludetheimplementationofGoodFriend:
:
hasAccess（）insitu,becauseitusesthefactthatHasStuffcontainsanintegernamedx（likewisefortheentireclassBestFriend）.Also,ifyoutriedtoaccessHasStuff:
:
xinGoodFriend:
:
hasNoAccess（）youwouldgetacompilererror.Thestatement“friendclassBestFriend”insideofHasStuffissimultaneouslyaforwarddeclarationandafrienddeclaration,otherwiseIwouldhavehadtoforward-declareBestFriendbeforethedefinitionofHasStuff（butI’mlazy）.
5-6
CreateaHenclass.Insidethis,nestaNestclass.InsideNest,placeanEggclass.Eachclassshouldhaveadisplay（）memberfunction.Inmain（）,createaninstanceofeachclassandcallthedisplay（）functionforeachone.
Solution:
//:
S05:
NestedFriends.cpp
#include
usingnamespacestd;
classHen{
public:
voiddisplay（）{
cout<<"Hen:
:
display\n";
}
classNest{
public:
voiddisplay（）{
cout<<"Hen:
:
Nest:
:
display\n";
}
classEgg{
public:
voiddisplay（）{
cout<<"Hen:
:
Nest:
:
Egg:
:
display\n";
}
};
};
};
intmain（）{
Henh;
Hen:
:
Nestn;
Hen:
:
Nest:
:
Egge;
h.display（）;
n.display（）;
e.display（）;
}
/*Output:
Hen:
:
display
Hen:
:
Nest:
:
display
Hen:
:
Nest:
:
Egg:
:
display
*/
///:
~
NestandEggarejustlikenormalclassesexcepttheyresideinthescopeofotherclassesinsteadoftheglobalscope,whichexplainstheneedfortheexplicitqualificationviathescoperesolutionoperator.Also,HenhasnoaccessrightstoanyprivatemembersofNestorEgg,nordoesNesthaveanyrightstoEgg’sprivatemembers（iftherewereany–seethenextexercise）.
5-7
ModifyExercise6sothatNestandEggeachcontainprivatedata.Grantfriendshiptoallowtheenclosingclassesaccesstothisprivatedata.
Solution:
//:
S05:
NestedFriends.cpp
#include
usingnamespacestd;
classHen{
public:
classNest{
intx;
friendclassHen;
public:
classEgg{
inty;
friendclassNest;
public:
voiddisplay（）{
cout<<"Hen:
:
Nest:
:
Egg:
:
display:
"<}
};
voidinitEgg（Egg*e）{
e->y=2;
}
voiddisplay（）{
cout<<"Hen:
:
Nest:
:
display:
"<}
};
voidinitNest（Nest*n）{
n->x=1;
}
voiddisplay（）{
cout<<"Hen:
:
display\n";
}
};
intmain（）{
Henh;
Hen:
:
Nestn;
Hen:
:
Nest:
:
Egge;
h.initNest（&n）;
n.initEgg（&e）;
h.display（）;
n.display（）;
e.display（）;
}
/*Output:
Hen:
:
display
Hen:
:
Nest:
:
display:
1
Hen:
:
Nest:
:
Egg:
:
display:
2
*/
///:
~
InthisexampleIhadtomovetheimplementationofHen:
:
Nest:
:
display（）pastthenestedclassEgg,becauseitaccessmembersofEgg.Thesamereasoningappliestotheinit-functionsabove.
5-8
Createaclasswithdatamembersdistributedamongnumerouspublic,private,andprotectedsections.AddamemberfunctionshowMap（）thatprintsthenamesofeachofthesedatamembersandtheiraddresses.Ifpossible,compileandrunthisprogramonmorethanonecompilerand/orcomputerand/oroperatingsystemtoseeiftherearelayoutdifferencesintheobject.
Here’sasamplefortwoparticularcompilers:
Solution:
//:
S05:
MapMembers.cpp
#include
usingnamespacestd;
classMapped{
intx;
protected:
inty;
public:
intz;
voidshowMap（）{
cout<<"xisat"<<&x<cout<<"yisat"<<&y<cout<<"zisat"<<&z<}
};
intmain（）{
Mappedm;
m.showMap（）;
}
/*Output:
//CompilerA:
xisat0065FDF8
yisat0065FDFC
zisat0065FE00
//CompilerB:
xisat0064FDEC
yisat0064FDF0
zisat0064FDF4
*/
///:
~
5-9
CopytheimplementationandtestfilesforStashinChapter4sothatyoucancompileandtestStash.hinthischapter.
（Lefttothereader）
5-10
PlaceobjectsoftheHenclassfromExercise6inaStash.Fetchthemoutandprintthem（ifyouhavenotalreadydoneso,youwillneedtoaddHen:
:
print（））.
（Lefttothereader）
5-11
CopytheimplementationandtestfilesforStackinChapter4sothatyoucancompileandtestStack2.hinthischapter.
（Lefttothereader）
5-12
PlaceobjectsoftheHenclassfromExercise6inaStack.Fetchthemoutandprintthem（ifyouhavenotalreadydoneso,youwillneedtoaddHen:
:
print（））.
（Lefttothereader）
5-13
ModifyCheshireinHandle.cpp,andverifythatyourprojectmanagerrecompilesandrelinksonlythisfile,butdoesn’trecompileUseHandle.cpp.
（Lefttothereader）
5-14
CreateaStackOfIntclass（astackthatholdsints）usingthe“Cheshirecat”techniquethathidesthelow-leveldatastructureyouusetostoretheelementsinaclasscalledStackImp.ImplementtwoversionsofStackImp:
onethatusesafixed-lengtharrayofint,andonethatusesavector.Haveapresetmaximumsizeforthestacksoyoudon’thavetoworryaboutexpandingthearrayinthefirstversion.NotethattheStackOfInt.hclassdoesn’thavetochangewithStackImp.
Solution:
Here’stheStackOfIntclass:
//:
S05:
StackOfInt.h
#include//forsize_t
#include//forINT_MIN
//VC++doesn’tputsize_tinstd:
#ifndef_MSC_VER
usingstd:
:
size_t;
#endif
structStackImp;//Incompletetypedeclaration
structStackOfInt{
enum{STKERROR=INT_MIN};
voidinit（）;
voidcleanup（）;
intpush（int）;
intpop（）;
inttop（）;
size_tsize（）;
private:
StackImp*pImpl;//The“smile”
};
///:
~
TodoCheshireCat,IjustdeclaretheStackImpclass（thismakesitan“incomplete”type）,anddeclareapointertoitasamemberofStackOfInt.TheimplementationsofStackOfInt’smemberfunctionswillusetheinternalsofStackImpviapImpl,soIhavetodefinethemethodbodiesinaseparate.cppfile（otherwisewe’renothidinganything!
）.Here’sthe.cppfileforthearrayversion:
//:
S05:
StackOfInt1.cpp{O}
//Usesanarraytoimplementastack
#include"StackOfInt.h"
//CompletetheincompletetypeStackImp:
//（Thiscouldbeinaseparateheaderfile）
structStackImp{
enum{MAXSIZE=100};
intdata[MAXSIZE];
intptr;
};
voidStackOfInt:
:
init（）{
pImpl=newStackImp;
}
intStackOfInt:
:
push（intx）{
if（pImpl->ptr==StackImp:
:
MAXSIZE）
returnSTKERROR;
e
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