coordin.h
// coordin.h -- structure templates and function prototypes
// structure templates
#ifndef COORDIN_H_
#define COORDIN_H_
struct polar
{
double distance; // distance from origin
double angle; // direction from origin
};
struct rect
{
double x; // horizontal distance from origin
double y; // vertical distance from origin
};
// prototypes
polar rect_to_polar(rect xypos);
void show_polar(polar dapos);
#endiffile1.cpp
// file1.cpp -- example of a three-file program
#include <iostream>
#include "coordin.h" // structure templates, function prototypes
using namespace std;
int main()
{
rect rplace;
polar pplace;
cout << "Enter the x and y values: ";
while (cin >> rplace.x >> rplace.y) // slick use of cin
{
pplace = rect_to_polar(rplace);
show_polar(pplace);
cout << "Next two numbers (q to quit): ";
}
cout << "Bye!\n";
// keep window open in MSVC++
/*
cin.clear();
while (cin.get() != '\n')
continue;
cin.get();
*/
return 0;
}
file2.cpp
// file2.cpp -- contains functions called in file1.cpp
#include <iostream>
#include <cmath>
#include "coordin.h" // structure templates, function prototypes
// convert rectangular to polar coordinates
polar rect_to_polar(rect xypos)
{
using namespace std;
polar answer;
answer.distance =
sqrt(xypos.x * xypos.x + xypos.y * xypos.y);
answer.angle = atan2(xypos.y, xypos.x);
return answer; // returns a polar structure
}
// show polar coordinates, converting angle to degrees
void show_polar(polar dapos)
{
using namespace std;
const double Rad_to_deg = 57.29577951;
cout << "distance = " << dapos.distance;
cout << ", angle = " << dapos.angle * Rad_to_deg;
cout << " degrees\n";
}
执行结果：
Enter the x and y values: 120 80
distance = 144.222, angle = 33.6901 degrees
Next two numbers (q to quit): 120 50
distance = 130, angle = 22.6199 degrees
Next two numbers (q to quit): q
Bye!autoscp.cpp
// autoscp.cpp -- illustrating scope of automatic variables
#include <iostream>
void oil(int x);
int main()
{
using namespace std;
int texas = 31;
int year = 2011;
cout << "In main(), texas = " << texas << ", &texas = ";
cout << &texas << endl;
cout << "In main(), year = " << year << ", &year = ";
cout << &year << endl;
oil(texas);//5 31 113 31
cout << "In main(), texas = " << texas << ", &texas = ";
cout << &texas << endl;
cout << "In main(), year = " << year << ", &year = ";
cout << &year << endl;
// cin.get();
return 0;
}
void oil(int x)
{
using namespace std;
int texas = 5;
cout << "In oil(), texas = " << texas << ", &texas = ";
cout << &texas << endl;
cout << "In oil(), x = " << x << ", &x = ";
cout << &x << endl;
{ // start a block
int texas = 113;
cout << "In block, texas = " << texas;
cout << ", &texas = " << &texas << endl;
cout << "In block, x = " << x << ", &x = ";//31
cout << &x << endl;
} // end a block
cout << "Post-block texas = " << texas;//5
cout << ", &texas = " << &texas << endl;
}
执行结果：
In main(), texas = 31, &texas = 00FCF764
In main(), year = 2011, &year = 00FCF758
In oil(), texas = 5, &texas = 00FCF670
In oil(), x = 31, &x = 00FCF684
In block, texas = 113, &texas = 00FCF664
In block, x = 31, &x = 00FCF684
Post-block texas = 5, &texas = 00FCF670
In main(), texas = 31, &texas = 00FCF764
In main(), year = 2011, &year = 00FCF758
external.cpp
// external.cpp -- external variable
// compile with support.cpp
#include <iostream>
// external variable
double warming = 0.3; // warming defined
// function prototypes
void update(double dt);
void local();
int main() // uses global variable
{
using namespace std;
cout << "Global warming is " << warming << " degrees.\n";
update(0.1); // call function to change warming
cout << "Global warming is " << warming << " degrees.\n";
local(); // call function with local warming
cout << "Global warming is " << warming << " degrees.\n";
// cin.get();
return 0;
}
support.cpp
// support.cpp -- use external variable
// compile with external.cpp
#include <iostream>
extern double warming; // use warming from another file
// function prototypes
void update(double dt);
void local();
using std::cout;
void update(double dt) // modifies global variable
{
extern double warming; // optional redeclaration
warming += dt; // uses global warming
cout << "Updating global warming to " << warming;
cout << " degrees.\n";
}
void local() // uses local variable
{
double warming = 0.8; // new variable hides external one
cout << "Local warming = " << warming << " degrees.\n";
// Access global variable with the
// scope resolution operator
cout << "But global warming = " << ::warming;
cout << " degrees.\n";
}
执行结果：
Global warming is 0.3 degrees.
Updating global warming to 0.4 degrees.
Global warming is 0.4 degrees.
Local warming = 0.8 degrees.
But global warming = 0.4 degrees.
Global warming is 0.4 degrees.twofile1.cpp
// twofile1.cpp -- variables with external and internal linkage
#include <iostream> // to be compiled with two file2.cpp
int tom = 3; // external variable definition
int dick = 30; // external variable definition
static int harry = 300; // static, internal linkage
// function prototype
void remote_access();
int main()
{
using namespace std;
cout << "main() reports the following addresses:\n";
cout << &tom << " = &tom, " << &dick << " = &dick, ";
cout << &harry << " = &harry\n";
remote_access();
// cin.get();
return 0;
}
twofile2.cpp
// twofile2.cpp -- variables with internal and external linkage
#include <iostream>
extern int tom; // tom defined elsewhere
static int dick = 10; // overrides external dick
int harry = 200; // external variable definition,
// no conflict with twofile1 harry
void remote_access()
{
using namespace std;
cout << "remote_access() reports the following addresses:\n";
cout << &tom << " = &tom, " << &dick << " = &dick, ";
cout << &harry << " = &harry\n";
}
执行结果：
main() reports the following addresses:
0072C000 = &tom, 0072C004 = &dick, 0072C008 = &harry
remote_access() reports the following addresses:
0072C000 = &tom, 0072C014 = &dick, 0072C010 = &harrystatic.cpp
// static.cpp -- using a static local variable
#include <iostream>
// constants
const int ArSize = 10;
// function prototype
void strcount(const char * str);
int main()
{
using namespace std;
char input[ArSize];
char next;
cout << "Enter a line:\n";
cin.get(input, ArSize);
while (cin)
{
cin.get(next);
while (next != '\n') // string didn't fit!
cin.get(next); // dispose of remainder
strcount(input);
cout << "Enter next line (empty line to quit):\n";
cin.get(input, ArSize);
}
cout << "Bye\n";
// code to keep window open for MSVC++
/*
cin.clear();
while (cin.get() != '\n')
continue;
cin.get();
*/
return 0;
}
void strcount(const char * str)
{
using namespace std;
static int total = 0; // static local variable
int count = 0; // automatic local variable
cout << "\"" << str << "\" contains ";
while (*str++) // go to end of string
count++;
total += count;
cout << count << " characters\n";
cout << total << " characters total\n";//静态变量total只是在程序运行时被设置为0
//以后在两次函数调用之间，其值将保持不变，所以能够记录读取的字符总数
}
执行结果：
Enter a line:
nice pants
"nice pant" contains 9 characters
9 characters total
Enter next line (empty line to quit):
thanks
"thanks" contains 6 characters
15 characters total
Enter next line (empty line to quit):
parting is such sweet sorrow
"parting i" contains 9 characters
24 characters total
Enter next line (empty line to quit):
ok
"ok" contains 2 characters
26 characters total
Enter next line (empty line to quit):
Byenewplace.cpp
// newplace.cpp -- using placement new
#include <iostream>
#include <new> // for placement new
const int BUF = 512;
const int N = 5;
char buffer[BUF]; // chunk of memory
int main()
{
using namespace std;
double *pd1, *pd2;
int i;
cout << "Calling new and placement new:\n";
pd1 = new double[N]; // use heap
pd2 = new (buffer) double[N]; // use buffer array
for (i = 0; i < N; i++)
pd2[i] = pd1[i] = 1000 + 20.0 * i;
cout << "Memory addresses:\n" << " heap: " << pd1
<< " static: " << (void *)buffer << endl;
cout << "Memory contents:\n";
for (i = 0; i < N; i++)
{
cout << pd1[i] << " at " << &pd1[i] << "; ";
cout << pd2[i] << " at " << &pd2[i] << endl;
}
cout << "\nCalling new and placement new a second time:\n";
double *pd3, *pd4;
pd3 = new double[N]; // find new address
pd4 = new (buffer) double[N]; // overwrite old data
for (i = 0; i < N; i++)
pd4[i] = pd3[i] = 1000 + 40.0 * i;
cout << "Memory contents:\n";
for (i = 0; i < N; i++)
{
cout << pd3[i] << " at " << &pd3[i] << "; ";
cout << pd4[i] << " at " << &pd4[i] << endl;
}
cout << "\nCalling new and placement new a third time:\n";
delete[] pd1;
pd1 = new double[N];
pd2 = new (buffer + N * sizeof(double)) double[N];
for (i = 0; i < N; i++)
pd2[i] = pd1[i] = 1000 + 60.0 * i;
cout << "Memory contents:\n";
for (i = 0; i < N; i++)
{
cout << pd1[i] << " at " << &pd1[i] << "; ";
cout << pd2[i] << " at " << &pd2[i] << endl;
}
delete[] pd1;
delete[] pd3;
// cin.get();
return 0;
}
执行结果：
Calling new and placement new:
Memory addresses:
heap: 010C9518 static: 00A5D2D8
Memory contents:
1000 at 010C9518; 1000 at 00A5D2D8
1020 at 010C9520; 1020 at 00A5D2E0
1040 at 010C9528; 1040 at 00A5D2E8
1060 at 010C9530; 1060 at 00A5D2F0
1080 at 010C9538; 1080 at 00A5D2F8
Calling new and placement new a second time:
Memory contents:
1000 at 010C9228; 1000 at 00A5D2D8
1040 at 010C9230; 1040 at 00A5D2E0
1080 at 010C9238; 1080 at 00A5D2E8
1120 at 010C9240; 1120 at 00A5D2F0
1160 at 010C9248; 1160 at 00A5D2F8
Calling new and placement new a third time:
Memory contents:
1000 at 010C9518; 1000 at 00A5D300
1060 at 010C9520; 1060 at 00A5D308
1120 at 010C9528; 1120 at 00A5D310
1180 at 010C9530; 1180 at 00A5D318
1240 at 010C9538; 1240 at 00A5D320namesp.h
// namesp.h
#include <string>
// create the pers and debts namespaces
namespace pers
{
struct Person
{
std::string fname;
std::string lname;
};
void getPerson(Person &);
void showPerson(const Person &);
}
namespace debts
{
using namespace pers;
struct Debt
{
Person name;
double amount;
};
void getDebt(Debt &);
void showDebt(const Debt &);
double sumDebts(const Debt ar[], int n);
}
namesp.cpp
// namesp.cpp -- namespaces
#include <iostream>
#include "namesp.h"
namespace pers
{
using std::cout;
using std::cin;
void getPerson(Person & rp)
{
cout << "Enter first name: ";
cin >> rp.fname;
cout << "Enter last name: ";
cin >> rp.lname;
}
void showPerson(const Person & rp)
{
std::cout << rp.lname << ", " << rp.fname;
}
}
namespace debts
{
void getDebt(Debt & rd)
{
getPerson(rd.name);
std::cout << "Enter debt: ";
std::cin >> rd.amount;
}
void showDebt(const Debt & rd)
{
showPerson(rd.name);
std::cout <<": $" << rd.amount << std::endl;
}
double sumDebts(const Debt ar[], int n)
{
double total = 0;
for (int i = 0; i < n; i++)
total += ar[i].amount;
return total;
}
}
usenmsp.cpp
// usenmsp.cpp -- using namespaces
#include <iostream>
#include "namesp.h"
void other(void);
void another(void);
int main(void)
{
using debts::Debt;
using debts::showDebt;
Debt golf = { {"Benny", "Goatsniff"}, 120.0 };
showDebt(golf);
other();
another();
// std::cin.get();
// std::cin.get();
return 0;
}
void other(void)
{
using std::cout;
using std::endl;
using namespace debts;
Person dg = {"Doodles", "Glister"};
showPerson(dg);
cout << endl;
Debt zippy[3];
int i;
for (i = 0; i < 3; i++)
getDebt(zippy[i]);
for (i = 0; i < 3; i++)
showDebt(zippy[i]);
cout << "Total debt: $" << sumDebts(zippy, 3) << endl;
return;
}
void another(void)
{
using pers::Person;;
Person collector = { "Milo", "Rightshift" };
pers::showPerson(collector);
std::cout << std::endl;
}
执行结果：
（选中3个执行文件进行编译）
Goatsniff, Benny: $120
Glister, Doodles
Enter first name: Arabella
Enter last name: Binx
Enter debt: 100
Enter first name: Cleve
Enter last name: Delaproux
Enter debt: 120
Enter first name: Eddie
Enter last name: Fiotox
Enter debt: 200
Binx, Arabella: $100
Delaproux, Cleve: $120
Fiotox, Eddie: $200
Total debt: $420
Rightshift, Milo
