C++ Tutorial/Function/function definition — различия между версиями
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Текущая версия на 10:29, 25 мая 2010
Содержание
- 1 Compare pass-by-value and pass-by-reference with references
- 2 Default arguments with parameters
- 3 Define function to add two parameters together
- 4 Definition of function template maximum
- 5 Functions in an expression: order of evaluation
- 6 Functions that take no arguments.
- 7 The function call stack and activation records
- 8 This program contains two functions: main() and f().
Compare pass-by-value and pass-by-reference with references
#include <iostream>
using std::cout;
using std::endl;
int byValue( int );
void byReference( int & );
int main()
{
int x = 2;
int z = 4;
cout << byValue( x ) << endl;
cout << "x = " << x << endl;
byReference( z );
cout << "z = " << z << endl;
return 0;
}
int byValue( int number )
{
return number *= number;
}
void byReference( int &numberRef )
{
numberRef *= numberRef;
}4 x = 2 z = 16
Default arguments with parameters
#include <iostream>
using std::cout;
using std::endl;
int f( int length = 1, int width = 1, int height = 1 );
int main()
{
cout << f();
cout << f( 10 );
cout << f( 10, 5 );
cout << f( 10, 5, 2 ) << endl;
return 0;
}
int f( int length, int width, int height )
{
return length * width * height;
}11050100
Define function to add two parameters together
#include <iostream>
int Add (int x, int y)
{
std::cout << "In Add(), received " << x << " and " << y << "\n";
return (x+y);
}
int main()
{
std::cout << "The value returned is: " << Add(3,4);
return 0;
}In Add(), received 3 and 4 The value returned is: 7
Definition of function template maximum
#include <iostream>
using std::cout;
using std::cin;
using std::endl;
template < class T >
T maximum( T value1, T value2, T value3 )
{
T maximumValue = value1;
if ( value2 > maximumValue )
maximumValue = value2;
if ( value3 > maximumValue )
maximumValue = value3;
return maximumValue;
}
int main()
{
int int1, int2, int3;
int1 = 1;
int2 = 2;
int3 = 3;
cout << "\nThe maximum integer value is: " << maximum( int1, int2, int3 );
double double1, double2, double3;
double1 = 1.1;
double2 = 2.2;
double3 = 3.3;
cout << "\nThe maximum double value is: "<< maximum( double1, double2, double3 );
char char1, char2, char3;
char1 = "a";
char2 = "b";
char3 = "c";
cout << "\nThe maximum character value is: "<< maximum( char1, char2, char3) << endl;
return 0;
}The maximum integer value is: 3 The maximum double value is: 3.3 The maximum character value is: c
Functions in an expression: order of evaluation
#include <iostream>
#include <ostream>
using namespace std;
int x = 1;
int f()
{
x = 2;
std::cout << "f()";
return x;
}
int g()
{
std::cout << "g()";
return x;
}
int main()
{
std::cout << f() / g() << "\n";
}f()g()1
Functions that take no arguments.
#include <iostream>
using std::cout;
using std::endl;
void f1();
void f2( void );
int main()
{
f1();
f2();
return 0;
}
void f1()
{
cout << "f1 takes no arguments" << endl;
}
void f2( void )
{
cout << "f2 also takes no arguments" << endl;
}f1 takes no arguments f2 also takes no arguments
The function call stack and activation records
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
int f( int );
int main()
{
int a = 10;
cout << a << " fd: " << f( a ) << endl;
return 0;
}
int f( int x )
{
return x * x;
}10 fd: 100
This program contains two functions: main() and f().
#include <iostream>
using namespace std;
void f(); // f"s protoype
int main()
{
cout << "In main()\n";
f(); // call f()
cout << "Back in main()\n";
return 0;
}
// This if the function"s definition.
void f()
{
cout << "Inside f()\n";
}In main() Inside f() Back in main()
