Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.NAME cout - Controls output to a stream buffer associated with the object stdout declared in <cstdio>.SYNOPSIS #include <iostream> extern ostream cout; ostream cout;DESCRIPTION The object cout controls output to a stream buffer associated with the object stdout declared in <cstdio>. By default the standard C and C++ streams are synchronized, but performance improvement can be achieved by using the ios_base member function synch_with_stdio to desynchronize them. After the object cin is initialized, cin.tie() returns &cout, which implies that cin and cout are synchronized.FORMATTING The formatting is done through member functions or manipulators. MANIPULATORS MEMBER FUNCTIONS showpos setf(ios_base::showpos) noshowpos unsetf(ios_base::showpos) showbase setf(ios_base::showbase) - 1 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 noshowbase unsetf(ios_base::showbase) uppercase setf(ios_base::uppercase) nouppercase unsetf(ios_base::uppercase) showpoint setf(ios_base::showpoint) noshowpoint unsetf(ios_base::showpoint) boolalpha setf(ios_base::boolalpha) noboolalpha unsetf(ios_base::boolalpha) unitbuf setf(ios_base::unitbuf) nounitbuf unsetf(ios_base::unitbuf) internal setf(ios_base::internal, ios_base::adjustfield) left setf(ios_base::left, ios_base::adjustfield) right setf(ios_base::right, ios_base::adjustfield) - 2 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 dec setf(ios_base::dec, ios_base::basefield) hex setf(ios_base::hex, ios_base::basefield) oct setf(ios_base::oct, ios_base::basefield) fixed setf(ios_base::fixed, ios_base::floatfield) scientific setf(ios_base::scientific, ios_base::floatfield) resetiosflags (ios_base::fmtflags flag) setf(0,flag) setiosflags (ios_base::fmtflags flag) setf(flag) setbase(int base) see above setfill(char_type c) fill(c) setprecision(int n) precision(n) setw(int n) width(n) - 3 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 endl ends flush flush( )DESCRIPTION showpos Generates a + sign in non-negative generated numeric output. showbase Generates a prefix indicating the numeric base of generated integer output uppercase Replaces certain lowercase letters with their uppercase equivalents in generated output showpoint Generates a decimal-point character unconditionally in generated floating-point output boolalpha Inserts and extracts bool type in alphabetic format unitbuf Flushes output after each output operation internal Adds fill characters at a designated internal point in certain generated output. If no such point is designated, it's identical to right. left Adds fill characters on the right (final positions) of certain generated output right Adds fill characters on the left (initial positions) of certain generated output - 4 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 dec Converts integer input or generates integer output in decimal base hex Converts integer input or generates integer output in hexadecimal base oct Converts integer input or generates integer output in octal base fixed Generates floating-point output in fixed-point notation scientific Generates floating-point output in scientific notation resetiosflags (ios_base::fmtflags flag) Resets the fmtflags field flag setiosflags (ios_base::fmtflags flag) Sets up the flag flag setbase(int base) Converts integer input or generates integer output in base base. The parameter base can be 8, 10 or 16. setfill(char_type c) Sets the character used to pad (fill) an output conversion to the specified field width setprecision(int n) Sets the precision (number of digits after the decimal point) to generate on certain output conversions - 5 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 setw(int n) Sets the field with (number of characters) to generate on certain output conversions showpos Generates a + sign in non-negative generated numeric output. showbase Generates a prefix indicating the numeric base of generated integer output uppercase Replaces certain lowercase letters with their uppercase equivalents in generated output showpoint Generates a decimal-point character unconditionally in generated floating-point output boolalpha Inserts and extracts bool type in alphabetic format unitbuf Flushes output after each output operation internal Adds fill characters at a designated internal point in certain generated output. If no such point is designated, it's identical to right. left Adds fill characters on the right (final positions) of certain generated output right Adds fill characters on the left (initial positions) of certain generated output - 6 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 dec Converts integer input or generates integer output in decimal base hex Converts integer input or generates integer output in hexadecimal base oct Converts integer input or generates integer output in octal base fixed Generates floating-point output in fixed-point notation scientific Generates floating-point output in scientific notation resetiosflags (ios_base::fmtflags flag) Resets the fmtflags field flag setiosflags (ios_base::fmtflags flag) Sets up the flag flag setbase(int base) Converts integer input or generates integer output in base base. The parameter base can be 8, 10 or 16. setfill(char_type c) Sets the character used to pad (fill) an output conversion to the specified field width setprecision(int n) Sets the precision (number of digits after the decimal point) to generate on certain output conversions - 7 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 setw(int n) Sets the field with (number of characters) to generate on certain output conversions endl Inserts a newline character into the output sequence and flush the output buffer. ends Inserts a null character into the output sequence. flush Flush the output buffer.DEFAULT VALUES precision() 6 width() 0 fill() the space character flags() skipws | dec getloc() locale::locale()EXAMPLE // // cout example #1 // #include<iostream> #include<iomanip> void main ( ) { using namespace std; int i; float f; // read an integer and a float from stdin cin >> i >> f; // output the integer and goes at the line cout << i << endl; // output the float and goes at the line - 8 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 cout << f << endl; // output i in hexa cout << hex << i << endl; // output i in octal and then in decimal cout << oct << i << dec << i << endl; // output i preceded by its sign cout << showpos << i << endl; // output i in hexa cout << setbase(16) << i << endl; // output i in dec and pad to the left with character // @ until a width of 20 // if you input 45 it outputs 45@@@@@@@@@@@@@@@@@@ cout << setfill('@') << setw(20) << left << dec << i; cout << endl; // output the same result as the code just above // but uses member functions rather than manipulators cout.fill('@'); cout.width(20); cout.setf(ios_base::left, ios_base::adjustfield); cout.setf(ios_base::dec, ios_base::basefield); cout << i << endl; // outputs f in scientific notation with // a precision of 10 digits cout << scientific << setprecision(10) << f << endl; // change the precision to 6 digits // equivalents to cout << setprecision(6); cout.precision(6); // output f and goes back to fixed notation cout << f << fixed << endl; } // // cout example #2 // #include <iostream> void main ( ) { using namespace std; - 9 - Formatted: June 20, 2006cout(3C++) Rogue Wave Software cout(3C++)- - 02 Apr 1998 char p[50]; cin.getline(p,50); cout << p; } // // cout example #3 // #include <iostream> #include <fstream> void main ( ) { using namespace std; // open the file "file_name.txt" // for reading ifstream in("file_name.txt"); // output the all file to stdout if ( in ) cout << in.rdbuf(); else { cout << "Error while opening the file"; cout << endl; } }WARNINGS Keep in mind that the manipulator endl flushes the stream buffer. Therefore it is recommended to use `/n' if your only intent is to go at the line. It greatly improves performance when C and C++ streams are not synchronized. If your compiler does not support namespaces, then you do not need the using declaration for std.SEE ALSO basic_ostream(3C++), basic_iostream(3C++), basic_filebuf(3C++), cin(3C++), cerr(3C++), clog(3C++), wcin(3C++), wcout(3C++), wcerr(3C++), wclog(3C++), iomanip(3C++)
//===========================================================================
void print(Date s){
cout.setfill('0');
cout<<setw(4)<<s.year<<'-'<<setw(2)<<s.month<<'-'<<setw(2)<<s.day<<'/n';
cout.setfill('');
}
//==============================================================================
上面的代码会报错。应该将cout.setfill改为cout<<setfill
注意：cout<<setfill('c') 引号间 必须有字符
