Thinking in C++ 2nd ed Volume 1 Revision 6

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more specific types of trash are derived that may have additional characteristics (a bottle has a color) or behaviors (an aluminum can may be crushed, a steel can is magnetic). In addition, some behaviors may be different (the value of paper depends on its type and condition). Using inheritance, you can build a type hierarchy that expresses the problem you’re trying to solve in terms of its types. A second example is the classic shape problem, perhaps used in a computer-aided design system or game simulation. The base type is “shape,” and each shape has a size, a color, a position, and so on. Each shape can be drawn, erased, moved, colored, etc. From this, specific types of shapes are derived (inherited): circle, square, triangle, and so on, each of which may have additional characteristics and behaviors. Certain shapes can be flipped, for example. Some behaviors may be different (calculating the area of a shape). The type hierarchy embodies both the similarities and differences between the shapes. Shape +draw() +erase() +move() +getColor() +setColor() Circle Square Triangle Casting the solution in the same terms as the problem is tremendously beneficial because you don’t need a lot of intermediate models to get from a description of the problem to a description of the solution. With objects, the type hierarchy is the primary model, so you go directly from the description of the system in the real world to the description of the system in code. Indeed, one of the difficulties people have with object-oriented 50 Thinking in C++ www.BruceEckel.com
design is that it’s too simple to get from the beginning to the end. A mind trained to look for complex solutions is often stumped by this simplicity at first. When you inherit from an existing type, you create a new type. This new type contains not only all the members of the existing type (although the private ones are hidden away and inaccessible), but more importantly it duplicates the interface of the base class. That is, all the messages you can send to objects of the base class you can also send to objects of the derived class. Since we know the type of a class by the messages we can send to it, this means that the derived class is the same type as the base class. In the above example, “a circle is a shape.” This type equivalence via inheritance is one of the fundamental gateways in understanding the meaning of objectoriented programming. Since both the base class and derived class have the same interface, there must be some implementation to go along with that interface. That is, there must be some code to execute when an object receives a particular message. If you simply inherit a class and don’t do anything else, the methods from the base-class interface come right along into the derived class. That means objects of the derived class have not only the same type, they also have the same behavior, which isn’t particularly interesting. You have two ways to differentiate your new derived class from the original base class. The first is quite straightforward: you simply add brand new functions to the derived class. These new functions are not part of the base class interface. This means that the base class simply didn’t do as much as you wanted it to, so you added more functions. This simple and primitive use for inheritance is, at times, the perfect solution to your problem. However, you should look closely for the possibility that your base class might also need these additional functions. This process of discovery and iteration of your design happens regularly in object-oriented programming. 1: Introduction to Objects 51
Page 1 and 2: Thinking in C++ 2 nd edition Volume
Page 3 and 4: TICA18: July 29, 1999. Rewrote Chap
Page 5 and 6: TICA7, August 14, 1998. Strings cha
Page 7 and 8: http://www.microsoft.com/typography
Page 9 and 10: In Bruce Eckel President, MindView
Page 11 and 12: MindView Ad Space
Page 13 and 14: Dedication To the scholar, the heal
Page 15 and 16: 2: Making & Using Objects 87 The pr
Page 17 and 18: Type-safe linkage............. 323
Page 19 and 20: protected ............. 618 protect
Page 21 and 22: Preface Like any human language, C+
Page 23 and 24: So the short answer is: what isn’
Page 25 and 26: end up losing some portion of the a
Page 27 and 28: Chapters C++ is a language in which
Page 29 and 30: Chapter 5: Hiding the Implementatio
Page 31 and 32: existing type. In this chapter you
Page 33 and 34: (and official mirror sites) where i
Page 35 and 36: note that the CD ROM is browser-bas
Page 37: Constantine, Lucy Lockwood, Tom Kef
Page 40 and 41: But computers are not so much machi
Page 42 and 43: the solution will run. There’s st
Page 44 and 45: So, although what we really do in o
Page 46 and 47: middle portion is not shown. If you
Page 48 and 49: necessary to achieve the functional
Page 52 and 53: Shape +draw() +erase() +move() +get
Page 54 and 55: Thermostat Controls Cooling System
Page 56 and 57: BirdController What happens when fl
Page 58 and 59: doStuff(c); What’s happening here
Page 60 and 61: The second approach is to create ob
Page 62 and 63: Analysis and design The object-orie
Page 64 and 65: It’s often proposed that you “b
Page 66 and 67: Phase 1: What are we making In the
Page 68 and 69: eveal itself in the fullness of tim
Page 70 and 71: getting into too much detail too ea
Page 72 and 73: 2. Object assembly. As you’re bui
Page 74 and 75: Phase 4: Iteration This is the poin
Page 76 and 77: will still function. You need not f
Page 78 and 79: You’re already on the learning cu
Page 80 and 81: large, complex program, there’s n
Page 82 and 83: first time, so it should not be mis
Page 84 and 85: Performance issues A common questio
Page 86 and 87: alternatives. Even if you eventuall
Page 88 and 89: By reading this chapter first, you
Page 90 and 91: takes several steps. The transition
Page 92 and 93: variable in another object module,
Page 94 and 95: point of definition the compiler al
Page 96 and 97: In a function declaration, you give
Page 98 and 99: cause the preprocessor to search fo
Page 100 and 101:
until link time, one possibility is
Page 102 and 103:
This book will use Standard C++ (an
Page 104 and 105:
included the header file but all th
Page 106 and 107:
"Hello, world!" And now, finally, t
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int main() { // Specifying formats
Page 110 and 111:
Simple file manipulation Standard I
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This upward compatibility from C to
Page 114 and 115:
iostream object. It’s that simple
Page 116 and 117:
it’s much easier if you have each
Page 118 and 119:
so if you have an array a and you w
Page 120 and 121:
while(in >> word) is what gets the
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Exercises Solutions to selected exe
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If you’ve never seen C before, th
Page 126 and 127:
} x = y = z; // ... It turns out th
Page 128 and 129:
In cfunc( ), the first if that eval
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to a nonzero value). Other conditio
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while(guess != secret) { // Compoun
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curly brace ‘{’. This is in con
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switch(selector) { case integral-va
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using namespace std; void removeHat
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: C03:AutoIncrement.cpp // Shows us
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The first part of the program defin
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: C03:Specify.cpp // Demonstrates t
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All the variables, and even the fun
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from dog, bird is four bytes away f
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: C03:PassByValue.cpp #include usi
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pointers later, but this is arguabl
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All possible combinations of basic
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variable was defined. That is, a sc
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int main() { //.. { // Begin a new
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using namespace std; int globe; voi
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want a value to be extant throughou
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} int i; // The data definition voi
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The const was taken from C++ and in
Page 168 and 169:
Operators and their use This sectio
Page 170 and 171:
Introduction to preprocessor macros
Page 172 and 173:
Bitwise not produces the opposite o
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An interesting bit pattern: unsigne
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x = a * -b; but the reader might ge
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Common pitfalls when using operator
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checking to catch errors. Once you
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(4) Implicit type conversions, norm
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Can't use xp as an X* at this point
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Keyword Meaning xor_eq ^= (bitwise
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The struct declaration must end wit
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int main() { Structure3 s1, s2; Str
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You can see how much more readable
Page 194 and 195:
Once you perform an assignment, the
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for(int i = 0; i < 10; i++) cout
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Even though func1( ) and func2( ) d
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#include using namespace std; int
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++, which “adds one to the pointe
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int* ip = a; P(*ip); P(*++ip); P(*(
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in all upper case. A common flag na
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punctuation are concatenated into a
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Defining a function pointer To defi
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Using a function pointer Once you d
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Make: an essential tool for separat
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multiple rules. Many make programs
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target1.exe: target2.exe: If you ju
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Declare: Declare.o $(CPP) $(OFLAG)D
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lectures, exercises, and guided sol
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values in your instance and print t
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flag. You will need to consult your
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to switch from some language that y
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:~ A tag name like CStashTag is gen
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delete []s->storage; } } ///:~ init
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new unsigned char[newBytes]; The ge
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: C04:CLibTest.cpp //{L} CLib // Te
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Each separate C file is a translati
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of all their function names. So ini
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C library converted to C++ // Decla
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You can see that all the member fun
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: C04:CppLibTest.cpp //{L} CppLib /
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What's an object Now that you’ve
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Object details A question that come
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most of the time, except when struc
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included throughout the system, the
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This will yield a true result, and
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end up “turning off” namespaces
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} void Stack::initialize() { head =
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Read file and store lines in the St
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etween what the user of the structu
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16. Modify Stash to use a vector as
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5: Hiding the Implementation A typi
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The second reason for access contro
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Although func( ) can access any mem
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void Z::initialize() { j = 99; } vo
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private: Holder* h; int* p; public:
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second argument) for n bytes past t
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Any object belonging to this class
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The examples in this book, however,
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void initialize(); void push(void*
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Here’s a simple example demonstra
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u.cleanup(); } ///:~ The only thing
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9. Copy the implementation and test
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This not only provides a single uni
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Now, when an object is defined, voi
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The destructor is called automatica
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eginning of a scope. If a construct
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However, some confusion may result
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pointer “down” (a relative term
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} storage = b; // Point to new memo
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Stack with constructors & destructo
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ut is not responsible for cleaning
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Now if you decide to add another el
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zz[i].print(); } ///:~ Notice that
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Safety during coding is a big issue
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7: Function Overloading & Default A
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Although function overloading is a
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int f(); This works fine when the c
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~Stash(); int add(void* element); v
Page 327 and 328:
Both constructors are exercised in
Page 329 and 330:
Although the member functions civil
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(outside all functions and classes)
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Placeholder arguments Arguments in
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Mem::Mem(int sz) { mem = 0; size =
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int main() { MyString s("My test st
Page 339 and 340:
Notice that a call to ensureMinSize
Page 341:
7. Create a new version of the Stac
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This provides safety and control in
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const). Storage must be allocated b
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situations, const means “a piece
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has the option of doing constant fo
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const int* const x = &d; // (1) int
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Function arguments & return values
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Returning by value as a const becom
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temporary X. However, f7( ) takes i
Page 360 and 361:
that attempting to modify the desti
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Error: const temporary created by f
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void print(); }; Fred::Fred(int sz)
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until Chapter 10: static. The stati
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The “enum hack” in old code In
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non-const member function. Thus, an
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cq.lastQuote(); // OK //! cq.quote(
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} int main() { const Z zz; zz.f();
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char Comm::read(int index) const {
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9. Write a const pointer to a doubl
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assign via a void* (without a cast)
Page 382 and 383:
In C, one of the ways to preserve e
Page 384 and 385:
granted. In the un-parenthesized ve
Page 386 and 387:
mixed together, so a problem like t
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space than the code generated to do
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Here, the class user never has dire
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void setWidth(int w) { width = w; }
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updateLocal(); return local.tm_sec;
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if(storage != 0) delete []storage;
Page 398 and 399:
The Stack class makes even better u
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Inlines & the compiler To understan
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class Forward { int i; public: Forw
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interface and thereby making the cl
Page 406 and 407:
Because there are actually two stat
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} } exit(1); inline void assure(std
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C++ is complicated enough without a
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second function, without the need f
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10: Name Control Creating names is
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function. C and C++ allow you to cr
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int i; public: X(int ii = 0) : i(ii
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static Obj b inside f( ) and the st
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all you’ve done is change the vis
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Creating a namespace The creation o
Page 427 and 428:
names in an unnamed namespace, you
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Integer a, b, c; Integer divide(Int
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} #endif // USINGDECLARATION_H ///:
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is not very safe. Global data can b
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ws.print(); } ///:~ Here, the quali
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static const X x3; static const X x
Page 439 and 440:
A static member function cannot acc
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int main() { //! Egg x(1); // Error
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zeroing of the storage occupied by
Page 445 and 446:
definition for the Initializer init
Page 447 and 448:
constructor, so you can tell if the
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} static Dependency1 dep1; return d
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across the various translation unit
Page 453 and 454:
that when you give the argument wit
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your namespace into that function s
Page 457:
a Mirror object, which it assigns t
Page 460 and 461:
Although references also exist in P
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2. Once a reference is initialized
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} ///:~ The call to f(1) produces a
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how does the compiler know how to p
Page 468 and 469:
farther to provide storage for the
Page 470 and 471:
output for bigfun( ), you can see i
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When the local object goes out of s
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} }; int HowMany2::objectCount = 0;
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cout.width(width); cout
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Temporary objects Line 15 begins th
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cout
Page 482 and 483:
Here’s an example: //: C11:NoCopy
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combined with the object dereferenc
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fp = &Simple2::f; } ///:~ In the de
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underlying implementation without a
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the member functions const and prov
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21. Create a simple class without a
Page 494 and 495:
The difference is that the argument
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} }; i += rv.i; return *this; int m
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operator++(Integer& a); // Postfix:
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} Byte operator!() const { cout
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an example of all the operators you
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friend int operator=(const Integer&
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if(&left == &right) {/* self-assign
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} #define TRYC(OP) \ out
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%= right.b; return *this; } Byte& o
Page 512 and 513:
} Byte b3 = 92; b1 = b2 = b3; int m
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ack the object that was changed. Th
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left-hand side of an equal sign. Th
Page 518 and 519:
class ObjContainer { vector a; publ
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#include #include "../require.h" u
Page 522 and 523:
pointer,” although the example sh
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around and calls operator( ) for th
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eturn i[x]; } friend ostream& opera
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Operator &= |= %= >>=
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When you create an operator=, you m
Page 532 and 533:
} ~Dog() { cout
Page 534 and 535:
it. However, if your object require
Page 536 and 537:
: p(dog), houseName(house) { cout
Page 538 and 539:
Before you make any modifications (
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Automatic operator= creation Becaus
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In this case, automatic type conver
Page 544 and 545:
Reflexivity One of the most conveni
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using namespace std; class Stringc
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: C12:TypeConversionFanout.cpp clas
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(the creator of the class) or the u
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16. Add an int data member to both
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13: Dynamic Object Creation Sometim
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Object creation When a C++ object i
Page 559 and 560:
... sometime later: obj->destroy();
Page 561 and 562:
with a call to free( )). Just as a
Page 563 and 564:
Before a pointer to that block is r
Page 565 and 566:
If you have a memory leak in your p
Page 567 and 568:
The other change is the replacement
Page 569 and 570:
can prevent a memory leak (more ele
Page 571 and 572:
However, for the string pointers, i
Page 573 and 574:
Now the array elements in q can be
Page 575 and 576:
Another issue is heap fragmentation
Page 577 and 578:
} free(m); class S { int i[100]; pu
Page 579 and 580:
} for(int i = 0; i < psize; i++) if
Page 581 and 582:
empty bracket syntax to indicate ar
Page 583 and 584:
In both cases you’re handed the s
Page 585 and 586:
When the program runs, it does not
Page 587 and 588:
Notice that operator new only retur
Page 589 and 590:
5. Repeat the above exercise, but a
Page 591 and 592:
14: Inheritance & Composition One o
Page 593 and 594:
int i; public: X() { i = 0; } void
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public: Y() { i = 0; } int change()
Page 597 and 598:
The solution is simple: Call the co
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This makes built-in types act a lit
Page 601 and 602:
#define CLASS(ID) class ID { \ publ
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properly reverse the order of the c
Page 605 and 606:
in the new class. In the next chapt
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Name hiding comes into play here be
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~GameBoard() { cout
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ecause that function was not explic
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implementation hiding themselves, s
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} operator ifstream&() { return fil
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inherit privately, you’re “impl
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int read() const { return i; } void
Page 621 and 622:
organic, evolutionary creature, rat
Page 623 and 624:
your diagrams any way you find help
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Child object to a Parent& (if you c
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#include #include using namespace
Page 629 and 630:
types inside the new type. Typicall
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class BusinessTraveler from Travele
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15: Polymorphism & Virtual Function
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quickly see the usefulness of this
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“narrow” that interface, but ne
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virtual void play(note) const { cou
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class Brass : public Wind { public:
Page 643 and 644:
The keyword virtual tells the compi
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pointer (the VPTR) into the structu
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instrument pointer brass object VPT
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call word ptr [bx+4] Finally, the s
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from the previous assembly-language
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instrument virtual void play() virt
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cout
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may be a common piece of code that
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virtual string sit() const { return
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the examples you’ve seen here, an
Page 663 and 664:
exists) and Dog, which no longer ex
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x = d2.f(); //! d2.f(s); // string
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int main() { Bird b; Cat c; Pet* p[
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Order of constructor calls The seco
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that is called last. This is anothe
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int main() { Base1* bp = new Derive
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The only distinction occurs when yo
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ely on portions of an object that h
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} Object* peek() const { return hea
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Creating containers that hold Objec
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using namespace std; class Shape {
Page 685 and 686:
picture” of class relationships.
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12. Create a model of a greenhouse
Page 689 and 690:
has no default constructor, so why
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16: Introduction to Templates Inher
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} int pop() { return stack[top > 0
Page 695 and 696:
need an object, create it with new,
Page 697 and 698:
object-based hierarchy with its con
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code. The container no longer holds
Page 701 and 702:
In main( ), you can see how easy it
Page 703 and 704:
people see software as a service, a
Page 705 and 706:
} }; class Number { float f; public
Page 707 and 708:
}* head; public: Stack() : head(0)
Page 709 and 710:
changeable throughout the lifetime
Page 711 and 712:
#ifndef AUTOCOUNTER_H #define AUTOC
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The destructor for CleanupCheck doe
Page 715 and 716:
in the program, and you don’t nec
Page 717 and 718:
int main() { Stack ac; // Ownership
Page 720 and 721:
array, copying the old array to the
Page 722 and 723:
of the underlying container) for an
Page 724 and 725:
} friend ostream& operator
Page 726 and 727:
} // Jump an iterator forward itera
Page 728 and 729:
void push(T* dat) { head = new Link
Page 730 and 731:
dereference operator performs the e
Page 732 and 733:
To create the end sentinel: iterato
Page 734 and 735:
} inflate(); storage[next++] = elem
Page 736 and 737:
int main() { { // To force destruct
Page 738 and 739:
class Square : public Shape { publi
Page 740 and 741:
drawAll(p); cout
Page 742 and 743:
that, to acquire a library from a t
Page 744 and 745:
16. (Advanced) Modify PointerToMemb
Page 746 and 747:
Although many of these issues have
Page 748 and 749:
Begin and end comment tags A very i
Page 750 and 751:
void func(int a) { you immediately
Page 752 and 753:
The issue of where to put the openi
Page 754 and 755:
Use of require( ) and assure( ) The
Page 756 and 757:
also from the insights of friends i
Page 758 and 759:
elationship where it doesn’t exis
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22. Don’t use private inheritance
Page 762 and 763:
than global variables, although you
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the heap, the catcher must know to
Page 766 and 767:
has enough information to deal with
Page 768 and 769:
768 Thinking in C++ www.BruceEckel.
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C Thinking in C: Foundations for Ja
Page 772 and 773:
Analysis & Design Extreme Programmi
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mathematical determinism and the il
Page 776 and 777:
# compiler under dos: { all } # Obj
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C07:MemTest.cpp C09:Cpptime.cpp C12
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Index -, 177 --, 178 !, 177 !=, 172
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linking compiled C code with C++, 4
Page 784 and 785:
declaration, 93, 245, 256 analyzing
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static member, 378, 440, 477 using
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Love, Tom, 777 lvalue, 170, 358 mac
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organization code, 260 code in head
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short, 145 side effect, 170, 178 si
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assembly-language code generated by
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