ceil这个函数很久之前使用过，不过忘了，今天又遇到了该函数。只是知道取整，是不小于还是不大于给忘了。
实际上，就是一个进一法得到的值，即，大于参数的最小整数值。
下面是一段测试代码：
＃i nclude
＃i nclude
using namespace std;
int main(int argc, char * argv[])
{
if(argc<2)
{
cout<<"usage: ceil 12.5"< return 1;
}
cout<
return 0;
}
下面是linux下的man page：
====================================
CEIL(3) Linux Programmer’s Manual CEIL(3)
NAME
ceil, ceilf, ceill - ceiling function: smallest integral value not less than argument
SYNOPSIS
＃i nclude
double ceil(double x);
float ceilf(float x);
long double ceill(long double x);
Link with -lm.
DESCRIPTION
These functions round x up to the nearest integer.
RETURN VALUE
The rounded integer value. If x is integral or infinite, x itself is returned.
ERRORS
No errors other than EDOM and ERANGE can occur. If x is NaN, then NaN is returned and errno may be set to
EDOM.
NOTES
SUSv2 and POSIX.1-2001 contain text about overflow (which might set errno to ERANGE, or raise an exception).
In practice, the result cannot overflow on any current machine, so this error-handling stuff is just nonsense.
(More precisely, overflow can happen only when the maximum value of the exponent is smaller than the number of
mantissa bits. For the IEEE-754 standard 32-bit and 64-bit floating point numbers the maximum value of the
exponent is 128 (resp. 1024), and the number of mantissa bits is 24 (resp. 53).)
CONFORMING TO
The ceil() function conforms to SVr4, POSIX.1-2001, 4.3BSD, C89, C99. The other functions are from C99.
SEE ALSO
floor(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3) |
