Pi的单/双/扩展精度浮点表示精确到小数位数？
#include
#define E_PI 3.1415926535897932384626433832795028841971693993751058209749445923078164062
int main(int argc, char** argv)
{
long double pild = E_PI;
double pid = pild;
float pif = pid;
printf("%s\n%1.80f\n%1.80f\n%1.80Lf\n",
"3.14159265358979323846264338327950288419716939937510582097494459230781640628620899",
pif, pid, pild);
return 0;
}
结果:
[quassnoi #] gcc --version
gcc (GCC) 4.3.2 20081105 (Red Hat 4.3.2-7)
[quassnoi #] ./test
3.14159265358979323846264338327950288419716939937510582097494459230781640628620899
3.14159274101257324218750000000000000000000000000000000000000000000000000000000000
^
3.14159265358979311599796346854418516159057617187500000000000000000000000000000000
^
3.14159265358979311599796346854418516159057617187500000000000000000000000000000000
^
0000000001111111
1234567890123456
当我检查Quassnoi的答案似乎可疑,我认为long double并double让我在一个小挖最终会得到相同的精度.如果我运行他用clang编译的代码,我得到了与他相同的结果.但是我发现如果我指定long double后缀并使用文字初始化long double,它提供了更多的精度.这是我的代码版本:
#include
int main(int argc, char** argv)
{
long double pild = 3.14159265358979323846264338327950288419716939937510582097494459230781640628620899L;
double pid = pild;
float pif = pid;
printf("%s\n%1.80f\n%1.80f\n%1.80Lf\n",
"3.14159265358979323846264338327950288419716939937510582097494459230781640628620899",
pif, pid, pild);
return 0;
}
结果如下:
3.14159265358979323846264338327950288419716939937510582097494459230781640628620899
3.14159274101257324218750000000000000000000000000000000000000000000000000000000000
^
3.14159265358979311599796346854418516159057617187500000000000000000000000000000000
^
3.14159265358979323851280895940618620443274267017841339111328125000000000000000000
^
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