向上取整：float ceilf(float); double ceil(double);
向下取整：float floorf(float); double floor(double);
四舍五入：float roundf(float); double round(double);
CGFloat a = 3.3;
CGFloat ceilA = ceilf(a);
CGFloat floorA = floorf(a);
CGFloat roundA = roundf(a);
NSLog(@"%lf 向上取整为%lf, 向下取整为%lf, 四舍五入为%lf", a, ceilA, floorA, roundA);
double b = 5.8;
double ceilB = ceil(b);
double floorB = floor(b);
double roundB = round(b);
NSLog(@"%lf 向上取整为%lf, 向下取整为%lf, 四舍五入为%lf", b, ceilB, floorB, roundB);
CGFloat c = -3.3;
CGFloat ceilC = ceilf(c);
CGFloat floorC = floorf(c);
CGFloat roundC = roundf(c);
NSLog(@"%lf 向上取整为%lf, 向下取整为%lf, 四舍五入为%lf", c, ceilC, floorC, roundC);
double d = -5.8;
double ceilD = ceil(d);
double floorD = floor(d);
double roundD = round(d);
NSLog(@"%lf 向上取整为%lf, 向下取整为%lf, 四舍五入为%lf", d, ceilD, floorD, roundD);
// 打印结果
2017-03-02 10:03:47.570 UsingWebView[88462:10650303] 3.300000 向上取整为4.000000, 向下取整为3.000000, 四舍五入为3.000000
2017-03-02 10:03:47.572 UsingWebView[88462:10650303] 5.800000 向上取整为6.000000, 向下取整为5.000000, 四舍五入为6.000000
2017-03-02 10:03:47.573 UsingWebView[88462:10650303] -3.300000 向上取整为-3.000000, 向下取整为-4.000000, 四舍五入为-3.000000
2017-03-02 10:03:47.573 UsingWebView[88462:10650303] -5.800000 向上取整为-5.000000, 向下取整为-6.000000, 四舍五入为-6.000000
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