Question

setw()与setprecision()的区别

我想请问一下setw(10)与setprecision(10)的区别～～～～
还有一个，width()~~~~~~

Answer 1

// 看看这个例子，分给楼上的。
可能你就明白了。

#include <iostream>
#include <iomanip>

using namespace std;

const double d1 = 1.23456789;
const double d2 = 12.3456789;
const double d3 = 123.456789;
const double d4 = 1234.56789;
const double d5 = 12345.6789;
const long l1 = 16;
const long l2 = 256;
const long l3 = 1024;
const long l4 = 4096;
const long l5 = 65536;
int base = 10;

void DisplayDefault( )
{
cout << endl << "default display" << endl;
cout << "d1 = " << d1 << endl;
cout << "d2 = " << d2 << endl;
cout << "d3 = " << d3 << endl;
cout << "d4 = " << d4 << endl;
cout << "d5 = " << d5 << endl;
}

void DisplayWidth( int n )
{
cout << endl << "fixed width display set to " << n << ".\n";
cout << "d1 = " << setw(n) << d1 << endl;
cout << "d2 = " << setw(n) << d2 << endl;
cout << "d3 = " << setw(n) << d3 << endl;
cout << "d4 = " << setw(n) << d4 << endl;
cout << "d5 = " << setw(n) << d5 << endl;
}

void DisplayLongs( )
{
cout << setbase(10);
cout << endl << "setbase(" << base << ")" << endl;
cout << setbase(base);
cout << "l1 = " << l1 << endl;
cout << "l2 = " << l2 << endl;
cout << "l3 = " << l3 << endl;
cout << "l4 = " << l4 << endl;
cout << "l5 = " << l5 << endl;
}

int main( int argc, char* argv[] )
{
DisplayDefault( );

cout << endl << "setprecision(" << 3 << ")" << setprecision(3);
DisplayDefault( );

cout << endl << "setprecision(" << 12 << ")" << setprecision(12);
DisplayDefault( );

cout << setiosflags(ios_base::scientific);
cout << endl << "setiosflags(" << ios_base::scientific << ")";
DisplayDefault( );

cout << resetiosflags(ios_base::scientific);
cout << endl << "resetiosflags(" << ios_base::scientific << ")";
DisplayDefault( );

cout << endl << "setfill('" << 'S' << "')" << setfill('S');
DisplayWidth(15);
DisplayDefault( );

cout << endl << "setfill('" << ' ' << "')" << setfill(' ');
DisplayWidth(15);
DisplayDefault( );

cout << endl << "setprecision(" << 8 << ")" << setprecision(8);
DisplayWidth(10);
DisplayDefault( );

base = 16;
DisplayLongs( );

base = 8;
DisplayLongs( );

base = 10;
DisplayLongs( );

return 0;
}

Answer 2

setw()设置位宽!就是你输出的东西要占多少位置!
setprecision()设置精度,有效数字就是!
另外控制符里没有width()好像!
width()是函数,作用与setw()一样的!

Answer 3

setw(10)设置输出宽度，补够10位
setprecision(10)设置输出精度，小数点的方面