*请直接去看原文,原文链接：https://blog.csdn.net/allanGold/article/details/102824921

isnan

• 如果一个数是一个确定的数，那它就不是nan值
• 如果一个数是无穷大，无穷小，那它就是nan值

if (isnan(1)) {
        DLog(@"1是NAN");
} else {
        DLog(@"1不是NAN");
}

abs

int abs(int i); // 处理int类型的取绝对值

fabs

double fabs(double i); //处理double类型的取绝对值

fabsf

float fabsf(float i);  /处理float类型的取绝对值

ceilf 进位方法

float numberToRound;
int result;
numberToRound = 5.61;
result = (int)ceilf(numberToRound);
NSLog(@"ceilf(%.2f) = %d", numberToRound, result);
//输出 ceilf(5.61) = 6

 numberToRound = 5.41;
 result = (int)ceilf(numberToRound);
 NSLog(@"ceilf(%.2f) = %d", numberToRound, result);
 //输出 ceilf(5.41) = 6

roundf 四舍五入

 float numberToRound;
int result;
numberToRound = 5.61;
result = (int)roundf(numberToRound);
NSLog(@"roundf(%.2f) = %d", numberToRound, result);
//输出 roundf(5.61) = 6

 numberToRound = 5.41;
 result = (int)roundf(numberToRound);
 NSLog(@"roundf(%.2f) = %d", numberToRound, result);
 //输出 roundf(5.41) = 5

floorf 模位方法

float numberToRound;
int result;
numberToRound = 5.61;
result = (int)floorf(numberToRound);
NSLog(@"floorf(%.2f) = %d", numberToRound, result);
//输出 floorf(5.61) = 5

 numberToRound = 5.41;
 result = (int)floorf(numberToRound);
 NSLog(@"floorf(%.2f) = %d", numberToRound, result);
 //输出 floorf(5.41) = 5