в 14:21, 25 мая 2010

2010-05-25T14:21:17Z

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2010-05-25T10:29:46Z

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==Ambiguous function call with function with default parameter value==

<source lang="cpp">#include <iostream>
using namespace std;
int myfunc(int i);
int myfunc(int i, int j=1);
int main()
{
cout << myfunc(4, 5) << " "; // unambiguous
//cout << myfunc(10); // ambiguous
return 0;
}
int myfunc(int i)
{
return i;
}
int myfunc(int i, int j)
{
return i*j;
}</source>
<pre class=codeResult>20 "</pre>

==Demonstrate default arguments==

<source lang="cpp">#include <iostream>
using namespace std;

void f(int x = 0, int y = 100);

int main()
{
f(1, 2);

f(10);

f();

return 0;
}

void f(int x, int y)
{
cout << "x: " << x << ", y: " << y << "\n";
}</source>
<pre class=codeResult>x: 1, y: 2
x: 10, y: 100
x: 0, y: 100</pre>

==demonstrates missing and default arguments==

<source lang="cpp">#include <iostream>
using namespace std;

void repchar(char="*", int=45);
int main(){
repchar();
repchar("=");
repchar("+", 30);
return 0;
}
void repchar(char ch, int n)
{
for(int j=0; j<n; j++)
cout << ch;
}</source>

==Function with two regular parameters and one parameter with default value==

<source lang="cpp">#include <iostream>
#include <cstring>
using namespace std;

void f(char *s1, char *s2, int len = 0);

int main()
{
char str1[80] = "This is a test";
char str2[80] = "0123456789";

f(str1, str2, 5);
f(str1, str2);
return 0;
}

void f(char *s1, char *s2, int len)
{
cout << s1;
cout << " " << len << " ";
cout << s2;
}</source>
<pre class=codeResult>This is a test 5 0123456789This is a test 0 0123456789</pre>

==Use two default parameter values==

<source lang="cpp">#include <iostream>

int f(int length, int width = 25, int height = 1);

int main()
{
int length = 100;
int width = 50;
int height = 2;
int area;

area = f(length, width, height);
std::cout << "First time area equals " << area << "\n";

area = f(length, width);
std::cout << "Second time area equals " << area << "\n";

area = f(length);
std::cout << "Third time area equals " << area << "\n";
return 0;
}

int f(int length, int width, int height)
{
return (length * width * height);
}</source>
<pre class=codeResult>First time area equals 10000
Second time area equals 5000
Third time area equals 2500</pre>

==Using multiple default parameter values: defaults for reference parameters==

<source lang="cpp">#include <iostream>
#include <iomanip>
#include <string>
using std::cout;
using std::endl;
using std::string;
void show_data(const int data[], int count = 1,
const string& title = "Data Values", int width = 10, int perLine =5);
int main() {
int data[] = {1, 2, 3, 4};
int dataItem = 99;
show_data (&dataItem);
dataItem = 13;
show_data(&dataItem, 1, "Unlucky for some!");
show_data(data, sizeof data/sizeof data[0]);
show_data(data, sizeof data/sizeof data[0], "title 1");
show_data(data, sizeof data/sizeof data[0], "title 2", 14);
show_data(data, sizeof data/sizeof data[0], "title 3", 14, 4);
return 0;
}
void show_data (const int data[], int count, const string& title,int width, int perLine) {
cout << endl << title;
cout << endl << perLine;
cout << endl << width << data[2];
cout << endl;
}</source>
<pre class=codeResult>Data Values
5
102
Unlucky for some!
5
102
Data Values
5
103
title 1
5
103
title 2
5
143
title 3
4
143</pre>

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