C++中浮點(diǎn)數(shù)的顯示很簡(jiǎn)單（默認(rèn)顯示小數(shù)點(diǎn)后5位且四舍五入），cout << fixed <<setPRecision(7) << area << endl;//小數(shù)點(diǎn)后面7位

                     但我想自己實(shí)現(xiàn)setprecision(7)函數(shù)，于是有如下代碼：

#include<iostream>#include<iomanip>using namespace std;int main()//輸出顯示7位小數(shù){	double number = 3.14159263358979323;	int lastnum = 0;	lastnum = ((int)(number * 100000000)) % 10;//小數(shù)點(diǎn)后面第8個(gè)數(shù)字	cout << lastnum << endl;	//四舍五入	if (lastnum >= 0 && lastnum <= 4)		number = ((int)(number * 10000000))*0.0000001;//第8位該舍	else if (lastnum >= 5 && lastnum <= 9)	{		number = (((int)(number * 10000000))*0.0000001) + 0.0000001;//第8位該入	}	cout << fixed << setprecision(7) << number << endl;	system("pause");	return(0);}