Бьярн Страустрап - Справочное руководство по C++

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();

}

#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";

}

#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";