в 14:21, 25 мая 2010

2010-05-25T14:21:17Z

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2010-05-25T10:28:56Z

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==An I/O manipulator: cout ==

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

int main()
{
cout << setprecision(2) << 1000.243 << endl;

return 0;
}</source>
<pre class=codeResult>1e+003</pre>

==An I/O manipulator: cout ==

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

int main()
{
cout << setw(20) << "Hello there.";

return 0;
}</source>
<pre class=codeResult>Hello there.</pre>

==Check cout flags==

<source lang="cpp">#include<iostream.h>
void showflags();
main()
{
showflags();
cout.setf(ios::oct|ios::showbase|ios::fixed);
showflags();
return 0;
}
void showflags()
{
long f;
char flgs[15][12]={
"skipws",
"left",
"right",
"internal",
"dec",
"oct",
"hex",
"showbase",
"showpoint",
"uppercase",
"showpos",
"scientific",
"fixed",
"unitbuf",
"stdio",
};
f=cout.flags();
for(int i=1,j=0;i<0x4000;i=i<<1,j++)
if(i&f)
cout<<flgs[j]<<"is on\n";
else
cout<<flgs[j]<<"is off\n";
cout<<"\n";
}</source>
<pre class=codeResult>skipwsis off
leftis on
rightis off
internalis off
decis off
octis off
hexis off
showbaseis off
showpointis off
uppercaseis off
showposis off
scientificis off
fixedis on
unitbufis off
skipwsis off
leftis on
rightis on
internalis off
decis off
octis off
hexis on
showbaseis off
showpointis off
uppercaseis on
showposis off
scientificis off
fixedis on
unitbufis off</pre>

==cout boolalpha: cause bool values to display as true or false==

<source lang="cpp">#include <iostream>
using std::boolalpha;
using std::cout;
using std::endl;
int main()
{
bool a = true;
bool b = false;
cout << boolalpha;
cout << "a = " << a << "; b = " << b;
return 0;
}</source>
<pre class=codeResult>a = true; b = false</pre>

==cout: fill()==

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

int main()
{
cout.setf(ios::showpos);
cout.setf(ios::scientific);
cout << 123 << " " << 123.23 << "\n";

cout.fill("#"); // fill using #
cout.width(10); // in a field of 10 characters
cout << 123 << " ";
cout.width(10); // set width to 10
cout << 123.23;

return 0;
}</source>
<pre class=codeResult>+123 +1.232300e+002
######+123 +1.232300e+002</pre>

==cout: flags() and unsetf()==

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

int main()
{
ios::fmtflags f;

f = cout.flags();

if(f & ios::showpos)
cout << "showpos is set for cout.\n";
else
cout << "showpos is cleared for cout.\n";

cout << "\nSetting showpos for cout.\n";
cout.setf(ios::showpos);

f = cout.flags();

if(f & ios::showpos)
cout << "showpos is set for cout.\n";
else
cout << "showpos is cleared for cout.\n";

cout << "\nClearing showpos for cout.\n";
cout.unsetf(ios::showpos);

f = cout.flags();

if(f & ios::showpos)
cout << "showpos is set for cout.\n";
else
cout << "showpos is cleared for cout.\n";

return 0;
}</source>
<pre class=codeResult>showpos is cleared for cout.
Setting showpos for cout.
showpos is set for cout.
Clearing showpos for cout.
showpos is cleared for cout.</pre>

==cout: precision()==

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

int main()
{
cout.setf(ios::showpos);
cout.setf(ios::scientific);
cout << 123 << " " << 123.23 << "\n";

cout.precision(2); // two digits after decimal point
cout.width(10); // in a field of 10 characters
cout << 123 << " ";
cout.width(10); // set width to 10
cout << 123.23 << "\n";

return 0;
}</source>
<pre class=codeResult>+123 +1.232300e+002
+123 +1.23e+002</pre>

==cout: setf()==

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

int main()
{
// Turn on showpos and scientific flags.
cout.setf(ios::showpos);
cout.setf(ios::scientific);

cout << 123 << " " << 123.23 << " ";

return 0;
}</source>
<pre class=codeResult>+123 +1.232300e+002</pre>

==cout.setf(ios::showpoint | ios::showpos, ios::showpoint);==

<source lang="cpp">#include <iostream>
using namespace std;
int main( )
{
cout.setf(ios::showpoint | ios::showpos, ios::showpoint);
cout << 100.0;
return 0;
}</source>
<pre class=codeResult>100.000</pre>

==cout: setiosflags()==

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

int main()
{
cout << setiosflags(ios::showpos) << setiosflags(ios::scientific) << 123 << 123.23;

return 0;
}</source>
<pre class=codeResult>+123 +1.232300e+002</pre>

==cout: unsetf==

<source lang="cpp">#include <iostream.h>
main(void)
{
cout.setf(ios::showpos);
cout.setf(ios::scientific);
cout << 123 << " "<< 123.456 << endl;
cout.precision(3);
cout.width(10);
cout << 123 << " "<< 123.456 << endl;;
cout.fill("#");
cout.width(10);
cout.unsetf(ios::scientific|ios::showpos);
cout.precision(5);
cout << 123 << " " << 123.456;
return 0;
}</source>
<pre class=codeResult>+123 +1.234560e+002
+123 +1.235e+002
#######123 123.46</pre>

==cout: width()==

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

int main()
{
cout.setf(ios::showpos);
cout.setf(ios::scientific);
cout << 123 << " " << 123.23 << "\n";

cout.precision(2); // two digits after decimal point
cout.width(10); // in a field of 10 characters
cout << 123 << " ";
cout.width(10); // set width to 10
cout << 123.23 << "\n";

return 0;
}</source>
<pre class=codeResult>+123 +1.232300e+002
+123 +1.23e+002</pre>

==Demonstrating left justification and right justification==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
using std::left;
using std::right;
#include <iomanip>
using std::setw;
int main()
{
int x = 12345;
cout << "Default is right justified:" << endl<< setw( 10 ) << x;
cout << "\n\nUse std::left to left justify x:\n"<< left << setw( 10 ) << x;

cout << "\n\nUse std::right to right justify x:\n"<< right << setw( 10 ) << x << endl;
return 0;
}</source>
<pre class=codeResult>Default is right justified:
12345
Use std::left to left justify x:
12345
Use std::right to right justify x:
12345</pre>

==Demonstrating stream-manipulators boolalpha and noboolalpha.==

<source lang="cpp">#include <iostream>
using std::boolalpha;
using std::cout;
using std::endl;
using std::noboolalpha;
int main()
{
bool booleanValue = true;
cout << "booleanValue is " << booleanValue << endl;
cout << "booleanValue (after using boolalpha) is "<< boolalpha << booleanValue << endl << endl;
booleanValue = false; // change booleanValue
cout << noboolalpha << endl; // use noboolalpha
cout << "booleanValue is " << booleanValue << endl;
cout << "booleanValue (after using boolalpha) is " << boolalpha << booleanValue << endl;
return 0;
}</source>
<pre class=codeResult>booleanValue is 1
booleanValue (after using boolalpha) is true

booleanValue is 0
booleanValue (after using boolalpha) is false</pre>

==Demonstrating the flags member function==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
using std::ios_base;
using std::oct;
using std::scientific;
using std::showbase;
int main()
{
int integerValue = 1000;
double doubleValue = 0.0947628;
cout << cout.flags() << "\n\n" << integerValue << "\t" << doubleValue << endl << endl;
ios_base::fmtflags originalFormat = cout.flags();
cout << showbase << oct << scientific;
cout << cout.flags() << "\n\n" << integerValue << "\t" << doubleValue << endl << endl;
cout.flags( originalFormat );
cout << cout.flags() << "\n\n" << integerValue << "\t" << doubleValue << endl;
return 0;
}</source>
<pre class=codeResult>4098
1000 0.0947628
011500
01750 9.476280e-002
4098
1000 0.0947628</pre>

==Fixed-point mode, show a "+" for positive nums, show 3 digits to the right of the decimal==

<source lang="cpp">#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main( ) {
ios_base::fmtflags flags = cout.flags( );
double pi = 3.14285714;
cout << "pi = " << fixed
<< showpos
<< setprecision(3)
<< pi << "\n";
cout.flags(flags);
}</source>
<pre class=codeResult>pi = +3.143</pre>

==ios::showpos | ios::showbase | ios::oct | ios::right==

<source lang="cpp">#include <iostream>
using namespace std;
void showflags();
int main()
{
// show default condition of format flags
showflags();
// showpos, showbase, oct, right are on, others off
ios::fmtflags f = ios::showpos | ios::showbase | ios::oct | ios::right;
cout.flags(f);
showflags();
return 0;
}

void showflags()
{
ios::fmtflags f;
long i;
f = cout.flags(); // get flag settings
// check each flag
for(i=0x4000; i; i = i >> 1)
if(i & f) cout << "1 ";
else cout << "0 ";
cout << " \n";
}</source>
<pre class=codeResult>0 0 1 0 0 0 0 0 0 0 0 0 0 1 0
0 0 0 1 0 1 0 1 1 0 0 0 0 0 0</pre>

==OR together two or more flags==

<source lang="cpp">#include <iostream>
using namespace std;
int main()
{
cout.setf(ios::showpoint | ios::showpos);
cout << 100.0;
return 0;
}</source>
<pre class=codeResult>+100.000</pre>

==Output a pointer==

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

int main()
{
char *ptr;

ptr = "Pointers add power to C++.\n";

cout << ptr;

return 0;
}</source>
<pre class=codeResult>Pointers add power to C++.</pre>

==parameterless manipulators that operate on output streams==

<source lang="cpp">Manipulator Purpose
boolalpha Turns on boolalpha flag.
endl Outputs a newline.
ends Outputs a null.
dec Turns on dec flag. Turns off the hex and oct flags.
fixed Turns on fixed flag. Turns off the scientific flag.
flush Flushes the stream.
hex Turns on hex flag. Turns off the dec and oct flags.
internal Turns on internal flag. Turns off the left and right flags.
left Turns on left flag. Turns off the right and internal flags.
noboolalpha Turns off boolalpha flag.
noshowbase Turns off showbase flag.
noshowpoint Turns off showpoint flag.
noshowpos Turns off showpos flag.
nounitbuf Turns off unitbuf flag.
nouppercase Turns off uppercase flag.
oct Turns on oct flag. Turns off the dec and hex flags.
right Turns on right flag. Turns off the left and internal flags.
scientific Turns on scientific flag. Turns off the fixed flag.
showbase Turns on showbase flag.
showpoint Turns on showpoint flag.
showpos Turns on showpos flag.
unitbuf Turns on unitbuf flag.
uppercase Turns on uppercase flag.

#include <iostream>
using namespace std;
void showflags(void);
int main(void)
{
showflags();
cout.setf(ios::right | ios::showpoint | ios::fixed);
showflags();
}
void showflags(void){
long flag_set, i;
int j;
char flags[15][12] = {
"skipws", "left", "right", "internal", "dec",
"oct", "hex", "showbase", "showpoint", "uppercase",
"showpos", "scientific", "fixed", "unitbuf",
};
flag_set = cout.flags();
for (i=1, j=0; i<0x2000; i = i<<1, j++)
if (i & flag_set)
cout << flags[j] << " is on." << endl;
else
cout << flags[j] << " is off." << endl;
cout << endl;
}</source>

==Printing a line of text with multiple statements==

<source lang="cpp">#include <iostream>
int main()
{
std::cout << "Welcome ";
std::cout << "to C++!\n";
return 0;
}</source>
<pre class=codeResult>Welcome to C++!</pre>

==Printing an integer with internal spacing and plus sign==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
using std::internal;
using std::showpos;
#include <iomanip>
using std::setw;
int main()
{
cout << internal << showpos << setw( 10 ) << 123 << endl;
return 0;
}</source>
<pre class=codeResult>+ 123</pre>

==Printing multiple lines of text with a single statement: use the \n==

<source lang="cpp">#include <iostream>
int main()
{
std::cout << "Welcome\nto\n\nC++!\n";
return 0;
}</source>
<pre class=codeResult>Welcome
to
C++!</pre>

==Scientific mode; don"t show plus sign anymore==

<source lang="cpp">#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
int main( ) {
ios_base::fmtflags flags = cout.flags( );
double pi = 3.14285714;
cout << "pi = " << scientific
<< noshowpos
<< pi << "\n";
cout.flags(flags);
}</source>
<pre class=codeResult>pi = 3.142857e+000</pre>

==Set cout to output hex==

<source lang="cpp">#include <iostream>
using namespace std;
int main()
{
cout.setf(ios::hex, ios::basefield);
cout << 100; // this displays 64
return 0;
}</source>
<pre class=codeResult>64</pre>

==setiosflags(ios::showpos); and setiosflags(ios::showbase);==

<source lang="cpp">#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
cout << setiosflags(ios::showpos);
cout << setiosflags(ios::showbase);
cout << 123 << " " << hex << 123;
return 0;
}</source>
<pre class=codeResult>+123 0x7b</pre>

==Set ios::showpoint, ios::showpos for double pointer number==

<source lang="cpp">#include <iostream>
using namespace std;
int main()
{
cout.setf(ios::showpoint);
cout.setf(ios::showpos);
cout << 100.0;
return 0;
}</source>
<pre class=codeResult>+100.000</pre>

==Show default condition of format flags==

<source lang="cpp">#include <iostream>
using namespace std;
void showflags() ;
int main()
{

showflags();
cout.setf(ios::right | ios::showpoint | ios::fixed);
showflags();
return 0;
}
void showflags()
{
ios::fmtflags f;
long i;
f = cout.flags(); // get flag settings
// check each flag
for(i=0x4000; i; i = i >> 1)
if(i & f) cout << "1 ";
else cout << "0 ";
cout << " \n";
}</source>
<pre class=codeResult>0 0 1 0 0 0 0 0 0 0 0 0 0 1 0
0 0 1 0 1 0 0 1 0 0 0 0 1 1 0</pre>

==Skip leading whitespace.==

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

int main()
{
char s[80];

cin >> ws >> s;
cout << s;

return 0;
}</source>
<pre class=codeResult>string string
string</pre>

==Stream-manipulator uppercase.==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
using std::hex;
using std::showbase;
using std::uppercase;
int main()
{
cout << uppercase << 4.345e10 << endl << hex << showbase << 123456789 << endl;
return 0;
}</source>
<pre class=codeResult>4.345E+010
0X75BCD15</pre>

==To use a parameterized manipulator, you must include <iomanip>. It defines the following manipulators:==

<source lang="cpp">resetiosflags (ios_base::fmtflags f) Turn off the flags specified in f.
setbase(int base) Set the number base to base.
setfill(int ch) Set the fill character to ch.
setiosflags(ios_base::fmtflags f) Turn on the flags specified in f.
setprecision (int p) Set the number of digits of precision.
setw(int w) Set the field width to w.</source>

==unset flag one by one==

<source lang="cpp">#include <iostream>
using namespace std;
int main()
{
cout.setf(ios::uppercase | ios::scientific);
cout << 100.12;
cout.unsetf(ios::uppercase);
cout << " \n" << 100.12;
return 0;
}</source>
<pre class=codeResult>1.001200E+002
1.001200e+002"</pre>

==Use function in cout statement==

<source lang="cpp">#include <iostream>
using namespace std;
int box(int length, int width, int height); // return the volume
int main()
{
// use the return value of box( ) directly
cout << "The volume is " << box(10.1, 11.2, 3.3);

return 0;
}
// This function returns a value.
int box(int length, int width, int height)
{
return length * width * height ;
}</source>
<pre class=codeResult>The volume is 330</pre>

==Use std::cout to output message to console==

<source lang="cpp">#include <iostream>
int main()
{
std::cout << "Hello World!\n";
return 0;
}</source>
<pre class=codeResult>Hello World!</pre>

==Use std::cout to output various data==

<source lang="cpp">#include <iostream>
int main()
{
std::cout << "test.\n";
std::cout << "Here is 5: " << 5 << "\n";
std::cout << "Here is a very big number:\t" << 70000;
std::cout << (float) 5/8 << std::endl;
std::cout << (double) 7000 * 7000 << std::endl;
std::cout << "a liiiiiiiiiiiiiiiiiiiiiiine\n";
return 0;
}</source>
<pre class=codeResult>test.
Here is 5: 5
Here is a very big number: 700000.625
4.9e+007
a liiiiiiiiiiiiiiiiiiiiiiine</pre>

==Use std::endl to output a new line sign==

<source lang="cpp">#include <iostream>
int main() {
int x = 5;
int y = 7;
std::cout << std::endl;
std::cout << x + y << " " << x * y;
std::cout << std::endl;
return 0;
}</source>
<pre class=codeResult>12 35</pre>

==use the setiosflags( ) manipulator to directly set the various format flags related to a stream.==

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

int main()
{
cout << setiosflags(ios::showpos);
cout << setiosflags(ios::showbase);
cout << 123 << " " << hex << 123;

return 0;
}</source>

==Using Manipulators to Format I/O==

<source lang="cpp">/*
Manipulator Purpose Input/Output
boolalpha Turns on boolapha flag. Input/Output
dec Turns on dec flag. Input/Output
endl Output a newline character and flush the stream. Output
ends Output a null. Output
fixed Turns on fixed flag. Output
flush Flush a stream. Output
hex Turns on hex flag. Input/Output
internal Turns on internal flag. Output
left Turns on left flag. Output
nobooalpha Turns off boolalpha flag. Input/Output
noshowbase Turns off showbase flag. Output
noshowpoint Turns off showpoint flag. Output
noshowpos Turns off showpos flag. Output
noskipws Turns off skipws flag. Input
nounitbuf Turns off unitbuf flag. Output
nouppercase Turns off uppercase flag. Output
oct Turns on oct flag. Input/Output
resetiosflags (fmtflags f) Turn off the flags specified in f. Input/Output
right Turns on right flag. Output
scientific Turns on scientific flag. Output
setbase(int base) Set the number base to base. Input/Output
setfill(int ch) Set the fill character to ch. Output
setiosflags(fmtflags f) Turn on the flags specified in f. Input/output
setprecision (int p) Set the number of digits of precision. Output
setw(int w) Set the field width to w. Output
showbase Turns on showbase flag. Output
showpoint Turns on showpoint flag. Output
showpos Turns on showpos flag. Output
skipws Turns on skipws flag. Input
unitbuf Turns on unitbuf flag. Output
uppercase Turns on uppercase flag. Output
ws Skip leading white space. Input
*/

#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
cout << hex << 100 << endl;

cout << setfill("?") << setw(10) << 2343.0;

return 0;
}</source>

==Using showpoint to control the printing of trailing zeros anddecimal points for doubles==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
using std::showpoint;
int main()
{
cout << "Before using showpoint" << endl
<< "9.9900 prints as: " << 9.9900 << endl
<< "9.9000 prints as: " << 9.9000 << endl
<< "9.0000 prints as: " << 9.0000 << endl << endl;
cout << showpoint
<< "After using showpoint" << endl
<< "9.9900 prints as: " << 9.9900 << endl
<< "9.9000 prints as: " << 9.9000 << endl
<< "9.0000 prints as: " << 9.0000 << endl;
return 0;
}</source>
<pre class=codeResult>Before using showpoint
9.9900 prints as: 9.99
9.9000 prints as: 9.9
9.0000 prints as: 9
After using showpoint
9.9900 prints as: 9.99000
9.9000 prints as: 9.90000
9.0000 prints as: 9.00000</pre>

==Using stream-manipulator showbase to show number base==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
using std::hex;
using std::oct;
using std::showbase;
int main()
{
int x = 100;
cout << "Printing integers preceded by their base:" << endl << showbase;
cout << x << endl; // print decimal value
cout << oct << x << endl; // print octal value
cout << hex << x << endl; // print hexadecimal value
return 0;
}</source>
<pre class=codeResult>Printing integers preceded by their base:
100
0144
0x64</pre>

==Using write().==

<source lang="cpp">#include <iostream>
#include <string.h>
using namespace std;
int main()
{
char One[] = "this is a test";
int fullLength = strlen(One);
int tooShort = fullLength -4;
int tooLong = fullLength + 6;
cout.write(One,fullLength) << "\n";
cout.write(One,tooShort) << "\n";
cout.write(One,tooLong) << "\n";
return 0;
}</source>

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