Бьярн Страустрап - Справочное руководство по C++

• Название: Справочное руководство по C++
• Автор: Бьярн Страустрап
• Жанр: Программирование

---

#include ‹string.h›

struct pair {

 char * name;

 int val;

};

class assoc {

 pair * vec;

 int max;

 int free;

public:

 assoc(int);

 int& operator[](char*);

 void print_all();

};

assoc::assoc(int s)

{

 max = (s‹16) ? s : 16;

 free = 0;

 vec = new pair[max];

}

int& assoc::operator[](char * p)

/*

 maintain a set of "pair"s

 search for p,

 return a reference to the integer part of its "pair"

 make a new "pair" if "p" has not been seen

*/

{

 register pair* pp;

 for (pp=&vec[free-1]; vec‹=pp; pp--)

  if (strcmp(p, pp-›name)-0) return pp-›val;

 if (free==max) {// overflow: grow the vector

  pair* nvec = new pair[max*2];

  for (int i=0; i‹max; i++) nvec[i] = vec[i];

  delete vec;

  vec = nvec;

  max = 2*max;

 }

 pp = &vec[free++];

 pp-›name = new char[strlen(p)+1];

 strcpy(pp-›name,p);

 pp-›val = 0;

 return pp-›val;

}

void assoc::print_all()

{

 for (int i=0; i‹free; i++)

  cout ‹‹ vec[i].name ‹‹ ": " ‹‹ vec[i].val ‹‹ "\n";

}

main()

{

 const MAX = 256;

 char buf[MAX];

 assoc vec(512);

 while (cin››buf) vec[buf]++;

 vec.print_all();

}

b6_8.cxx

#include ‹stream.hxx›

#include ‹string.h›

struct pair {

 char* name;

 int val;

};

class assoc {

 friend class assoc_iterator;

 pair* vec;

 int max;

 int free;

public:

 assoc(int);

 int& operator[](char*);

};

class assoc_iterator {

 assoc* cs;

 int i;

public:

 assoc_iterator(assoc& s) { cs =&s; i = 0; }

 pair* operator()()

 { return (i‹cs-›free) ? &cs-›vec[i++] : 0; }

};

assoc::assoc(int s)

{

 max = (s‹16) ? s : 16;

 free = 0;

 vec = new pair[max];

}

int& assoc::operator[](char* p)

{

 register pair* pp;

 for (pp = &vec[free-1]; vec‹=pp; pp--)

  if (strcmp(p,pp-›name)==0) return pp-›val;

 if (free == max) {

  pair* nvec = new pair[max*2];

  for (int i=0; i‹max; i++) nvec[i] = vec[i];

  delete vec;

  vec = nvec;

  max = 2*max;

 }

 pp =&vec[free++];

 pp-›name = new char[strlen(p)+1];

 strcpy(pp-›name,p);

 pp-›val = 0;

 return pp-›val;

}

main()

{

 const MAX = 256;

 char buf[MAX];

 assoc vec(512);

 while (cin››buf) vec[buf]++;

 assoc_iterator next(vec);

 pair* p;

 while (p = next())

  cout ‹‹ p-›name ‹‹ ": " ‹‹ p-›val ‹‹ "\n";

}

b6_9.cxx

#include ‹stream.hxx›

#include ‹string.h›

extern void exit(int);

class string {

 struct srep {

  char* s;

  int n;

 };

 srep *p;

public:

 string(char *);

 string();

 string(string&);

 string& operator=(char *);

 string& operator=(string&);

 ~string();

 char& operator[](int i);

 friend ostream& operator‹‹(ostream&, string&);

 friend istream& operator››(istream&, string&);

 friend int operator==(string&x, char *s)

  { return strcmp(x.p-›s, s) == 0; }

 friend int operator==(string&x, string&y)

  { return strcmp(x.p-›s, y.p-›s) == 0; }

 friend int operator!=(string&x, char *s)

  {return strcmp(x.p-›s, s) != 0;}

 friend int operator!=(string&x, string&y)

  {return strcmp (x.p-›s, y.p-›s) != 0;}

};

string::string()

{

 p = new srep;

 p-›s = 0;

 p-›n = 1;

}

string::string(char* s)

{

 p = new srep;

 p-›s = new char[strlen(s) +1];

 strcpy(p-›s, s);

 p-›n = 1;

}

string::string(string& x)

{

 x.p-›n++;

 p = x.p;

}

string::~string()

{

 if (--p-›n - 0) {

  delete p-›s;

  delete p;

 }

}

string& string::operator=(char* s)

{

 if (p-›n › 1) {

  p-›n--;

  p = new srep;

 }

 else if (p-›n == 1)

  delete p-›s;

 p-›s = new char[strlen(s)+1];

 strcpy(p-›s, s);

 p-›n = 1;

 return *this;

}

string& string::operator=(string& x)

{

 x.p-›n++;

 if (--p-›n == 0) {

  delete p-›s;

  delete p;

 }

 p = x.p;

 return *this;

}

ostream& operator‹‹(ostream& s, string& x)

{

 return s ‹‹ x.p-›s ‹‹ " [" ‹‹ x.p-›n ‹‹ "]\n";

}

istream& operator››(istream& s, string& x)

{

 char buf[256];

 s››buf;

 x = buf;

 cout ‹‹ "echo: " ‹‹ x ‹‹ "\n";

 return s;

}

void error(char* p)

{

 cout ‹‹ p ‹‹ "\n";

 exit(1);

}

char& string::operator[](int i)

{

 if (i‹0 || strlen(p-›s)‹i) error("index out of range");

 return p-›s[i];

}

main()

{

 string x[100];

 int n;

 cout ‹‹ "here we go\n";

 for (n = 0; cin››x[n]; n++) {

  string y;

  if (n==100) error("too many strings");

  cout ‹‹ (y = x[n]);

  if (y=="done") break;

 }

 cout ‹‹ "here we go back again\n";

 for (int i=n-1; 0‹=i; i--) cout ‹‹ x[i];

}

b7_2_8.cxx

#include ‹stream.hxx›

struct employee {

 friend class manager;

 employee* next;

 char* name;

 short department;

 virtual void print();

};

struct manager: employee {

 employee* group;

 short level;

 void print();

};

void employee::print()

{

 cout ‹‹ name ‹‹ "\t" ‹‹ department ‹‹ "\n";

}

void manager::print()

{

 employee::print();

 cout ‹‹ "\tlevel " ‹‹ level ‹‹ "\n";

}

void f(employee* ll)

{

 for (; ll; ll=ll-›next) ll-›print();

}

main ()

{

 employee e;

 e.name = "J. Brown";

 e.department = 1234;

 e.next = 0;

 manager m;

 m.name = "J. Smith";

 m.department = 1234;

 m.level = 2;

 m.next = &e;

 f(&m);

}

b7_7.cxx

#include ‹stream.hxx›

struct base { base(); };

struct derived: base { derived(); };

base:: base()

{

 cout ‹‹ "\tbase 1: this=" ‹‹ long(this) ‹‹ "\n";

 if (this == 0) this = (base*)27;

 cout ‹‹ "\tbase 2: this=" ‹‹ long(this) ‹‹ "\n";

}

derived::derived()

{

 cout ‹‹ "\tderived 1: this=" ‹‹ long(this) ‹‹ "\n";

 if (this == 0) this = (derived*)43;

 cout ‹‹ "\tderived 2: this=" ‹‹ long(this) ‹‹ "\n";

}

main()

{

 cout ‹‹ "base b;\n";

 base b;

 cout ‹‹ "new base;\n";

 new base;

 cout ‹‹ "derived d;\n";

 derived d;

 cout ‹‹ "new derived;\n";

 new derived;

 cout ‹‹ "new derived;\n";

 new derived;

 cout ‹‹ "at the end\n";

}

b8_3_3.cxx

#include ‹xstream.hxx›

extern void exit(int);

void error(char* s, char* s2)

{

 cerr ‹‹ s ‹‹ " " ‹‹ s2 ‹‹ "\n";

 exit(1);

}

main(int argc, char* argv[])

{

 if (argc != 3) error ("wrong number of arguments",");

 filebuf f1;

 if (f1.open(argv[1],input) == 0)

  error("cannot open input file",argv[1]);

 istream from(&f1);

 filebuf f2;

 if (f2.open(argv[2],output) == 0)

  error("cannot open input file",argv[2]);

 ostream to(&f2);

 char ch;

 while (from.get(ch)) to.put(ch);

 if (!from.eof() || to.bad())

  error("something strange happened",");

}

Примечания

1

"The C Programming Language" B. Kernighan, D. Ritchie. Prentice Hall, 1978, 1988. Есть русский перевод: "Язык программирования С. Задачи по языку С" Б. Керниган, Д. Ритчи, А. Фьюер. "Финансы и статистика". 1984