数字处理
目录1. cell/floor(向上/向下取整)
use POSIX qw(ceil floor);
#向上取整
print ceil(5.5); # 6
print ceil(6) ; # 6
print ceil(6.1); # 7
print ceil(6.5); # 7
#向下取整
print floor(5.5); # 5
print floor(6) ; # 6
print floor(6.1); # 6
print floor(6.5); # 6