C++ Tutorial/Data Types/double output — различия между версиями
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Версия 17:21, 25 мая 2010
Содержание
After setting the showpos and showpoint flags
<source lang="cpp">#include <iostream>
- include <iomanip>
using namespace std; int main() {
cout << "Default format: " << 123.123456789 << endl; cout << "Default: " << 10.0 << endl; cout << "After setting the showpos and showpoint flags: "; cout << showpos << showpoint << 10.0 << "\n\n"; return 0;
}</source>
Precision of double: setprecision
<source lang="cpp">#include <iomanip>
- include <iostream>
using namespace std; int main( ){
const double x = .39; const double y = 27; cout<< ".39, fixed, 1 decimal place: " << fixed << setprecision( 1 ) << x << endl << ".39, fixed, 2 decimal places: " << setprecision( 2 ) << x << endl << ".39, fixed, 3 decimal places: " << setprecision( 3 ) << x << endl << endl << ".39, scientific, 1 decimal place: " << scientific << setprecision( 1 ) << x << endl << ".39, scientific, 2 decimal places: " << setprecision( 2 ) << x << endl << ".39, scientific, 3 decimal places: " << setprecision( 3 ) << x << endl << endl // return to default floating-point output format << resetiosflags( ios::fixed | ios::scientific ) << setprecision( 6 ) << ".39 and 27., default: " << x << " " << y << endl << ".39 and 27., default, 1 decimal place: " << setprecision( 1 ) << x << " " << y << endl << ".39 and 27., default, 2 decimal places: " << setprecision( 2 ) << x << " " << y << endl << ".39 and 27., default, 3 decimal places: " << setprecision( 3 ) << x << " " << y << endl << endl << ".39 and 27., default, decimal point: " << showpoint << x << " " << y << endl << ".39 and 27., default, decimal point, 1 decimal place: " << setprecision( 1 ) << x << " " << y << endl << ".39 and 27., default, decimal point, 2 decimal places: " << setprecision( 2 ) << x << " " << y << endl << ".39 and 27., default, decimal point, 3 decimal places: " << setprecision( 3 ) << x << " " << y << endl;
}</source>
Return to default format
<source lang="cpp">#include <iostream>
- include <iomanip>
using namespace std; int main() {
cout << "Default format: " << 123.123456789 << endl; cout << "Scientific format with precision of 7: "; cout << scientific << 123.123456789 << endl; cout << "Return to default format: "; cout << resetiosflags(ios::floatfield) << setprecision(6) << 123.123456789 << "\n\n"; return 0;
}</source>
setw manipulator is useful when repeated field
<source lang="cpp">#include <iostream>
- include <iomanip>
using namespace std; int main() {
cout << "Default format: " << 123.123456789 << endl; cout << "setw manipulator is useful when repeated field\n" << "widths must be specified. For example:\n"; cout << setw(8) << "this" << endl << setw(8) << "is" << endl << setw(8) << "a" << endl << setw(8) << "column" << endl << setw(8) << "of" << endl << setw(8) << "words"; return 0;
}</source>
Use a field width of 20
<source lang="cpp">#include <iostream>
- include <iomanip>
using namespace std; int main() {
cout << "Default format: " << 123.123456789 << endl; cout << "Use a field width of 20:\n"; cout << "|" << setw(20) << "Testing" << "|\n\n"; cout << "Use a field width of 20 with left justification:\n"; cout << "|" << setw(20) << left << "Testing" << "|\n\n"; return 0;
}</source>