Objective-C浮点数转化整数（向上取整、向下取整）

Objective-C拓展了C,自然很多用法是和C一致的。比如浮点数转化成整数，就有以下四种情况。 
1.简单粗暴，直接转化

float f = 1.5;
int a;
a = (int)f;
NSLog("a = %d",a);

输出结果是1。（int）是强制类型转化，丢弃浮点数的小数部分。

2.高斯函数，向下取整

float f = 1.5;
int a;
a = ceil(f);
NSLog("a = %d",a);

 

输出结果是1。floor()方法是向下取整，类似于数学中的高斯函数 [].取得不大于浮点数的最大整数，对于正数来说是舍弃浮点数部分，对于复数来说，舍弃浮点数部分后再减1.

3.ceil函数，向上取整。

float f = 1.5;
int a;
a = ceil(f);
NSLog("a = %d",a);

输出结果是2。ceil()方法是向上取整，取得不小于浮点数的最小整数，对于正数来说是舍弃浮点数部分并加1，对于复数来说就是舍弃浮点数部分.

4.通过强制类型转换四舍五入。

float f = 1.5;
int a;
a = (int)(f+0.5);
NSLog("a = %d",a);

其中原理非常简单，所以就不做详细说明了。

5.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");
}

6.abs

int abs(int i); // 处理int类型的取绝对值

7.fabs

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

8.fabsf

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

9.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

10.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

11.roundf 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

https://blog.youkuaiyun.com/abc649395594/article/details/44730425

https://www.jianshu.com/p/236825b712fe