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PHP服务性能优化总结

萨摩斯加士奇 03-06 13:00 阅读 4

例:TruncRealNum()模板函数 对实数进行截断保留n位小数
输入: double d = 3.14159265358979;
float f = 3.141592635
输出: d = TruncRealNum(d,5);
d = 3.14159
f = TruncRealNum(f,4);
f = 3.1416

#include <iostream>
#include <cmath>
#include <iomanip>

using namespace std;

template <typename RealType>			//模板支持float,double
RealType TruncRealNum(RealType num, int precision)
{
	if (precision < 0)
	{
		return num;
	}

	if (0 == precision)
	{
		return round(num);
	}

	int anum = static_cast<int>((num + 0.5 * pow(0.1, precision)) * pow(10, precision));			//被舍去的一位四舍五入进位
	std::cout<<std::setprecision(precision +  1);       //调整输出流的显示精度
	return static_cast<RealType>(anum / pow(10, precision));
}

例子: main函数

int main(){

	
    float f = 3141592654;
	double d = 3.456343424523547867;

	std::cout<<std::setprecision(16)<<endl;
	cout<<f<<" "<<d<<endl;
	cout << TruncRealNum(f, 0) << endl;
	cout << TruncRealNum(f, 1) << endl;
	cout << TruncRealNum(f, 4) << endl;
	cout<<"---------------------------"<<endl;
	cout<<TruncRealNum(d,0)<<endl;
	double d4 = TruncRealNum(d,4);
	cout<<d4<<endl;
	double d8 = TruncRealNum(d,15);
	cout<<d8<<endl;

    return 0;
}
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