关于输入输出的问题

[w66187564]

以下一段代码：
#include <iostream>
using namespace std;
void main()
{
class point
{
public:
void setx(double px)
{
x=px;
}
void sety(double py)
{
y=py;
}
void printpoint()
{
cout<<"x="<<x<<",y="<<y<<endl;
}
private:
double x;
double y;
};
point p;
p.sety(7.0);
p.setx(4.0);
p.printpoint();
}
输出结果为什么是4和7而不是4.0和7.0呢？
x和y不是都是double类型的吗？

[laolaoliu2002]

double x;
double y;
就要输出4.0&7.0了.

[laolaoliu2002]

Double precision values with double type have 8 bytes. The format is similar to the float format except that it has an 11-bit excess-1023 exponent and a 52-bit mantissa, plus the implied high-order 1 bit. This format gives a range of approximately 1.7E–308 to 1.7E+308 for type double.

Microsoft Specific

The double type contains 64 bits: 1 for sign, 11 for the exponent, and 52 for the mantissa. Its range is +/–1.7E308 with at least 15 digits of precision.

[珍惜生命远离CPP]

你看一下这个例子.

#include <iostream>

int main( ) 
{
   using namespace std;
   double f1= 5.000;
   cout << f1 << endl;   // noshowpoint is default
   cout.precision( 4 );
   cout << showpoint << f1 << endl;
   cout << noshowpoint << f1 << endl;
}

输出
5
5.000
5

[Mnky]

cout<<"x="<<setprecision(1)<<x;

[arong1234]

为什么不是4.00, 而要4.0?

[laolaoliu2002]

你可以控制输出多少,你输入的就是4.0&7.0