iOS：常用的Math函数

1、取整数

向上取整数

ceil(_: Double) -> Double

向下取整数

floor(_: Double) -> Double

四舍五入取整数

round(_: Double) -> Double

直接去掉数字的小数部分

trunc(_: Double) -> Double

let floatNum = 3.1415926
print("ceil = \(ceil(floatNum))， floor = \(floor(floatNum)), round = \(round(floatNum))")
print("trunc\(trunc(-6.534))")
输出：
ceil = 4.0， floor = 3.0, round = 3.0
trunc = 6.0

2、求绝对值

浮点数求绝对值

fabs(_: Double) -> Double

整数求绝对值

func abs<T>(_ x: T) -> T where T : Comparable, T : SignedNumeric

此函数可以根据T的类型，求对应的绝对值

let oneNum = -3.14
let oneInt = -4
print("fabs = \(fabs(oneNum)) abs = \(abs(oneInt))")

输出：fabs = 3.14 abs = 4

3、指数与对数

求取自然数e的幂

exp(_ x: Double) -> Double

开平方

sqrt(_: Double) -> Double

求以e为底的对数

log(_ x: Double) -> Double

求以2为底的对数

log2(_ x: Double) -> Double

求以10为底的对数

log10(_ x: Double) -> Double

计算以x为底数的y次幂

pow(_: Double, _: Double) -> Double

let twoNum = 2.0
print("exp = \(exp(twoNum)), sqrt = \(sqrt(twoNum))\n log = \(log(twoNum)), log2 = \(log2(twoNum)), log10 = \(log10(twoNum)) \npow = \(pow(twoNum, 3))")

输出：
exp = 7.38905609893065, sqrt = 1.4142135623730951
log = 0.6931471805599453 log2 = 1.0 log10 = 0.3010299956639812 
pow = 8.0

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