极值

# 编程语言极值

# C语言

limits.h

CHAR_BIT //char的二进制位数(bit)

CHAR_MAX //char的有符号整数最大值

CHAR_MIN //char的有符号整数最小值

MB_LEN_MAX //多字节字符的最大字节(byte)数

LONG_MAX //long的十进制最大值

LONG_MIN //long的十进制最小值

SCHAR_MAX //signedchar的十进制整数最大值

SCHAR_MIN //signedchar的十进制整数最小值

SHRT_MIN //short的十进制最小值

SHRT_MAX //short的十进制最大值

UCHAR_MAX //unsignedchar的十进制整数最大值

UINT_MAX //unsignedint的十进制最大值

ULONG_MAX //unsignedlongint的十进制最大值

USHRT_MAX //unsignedshortint的十进制最大值

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需要关注的有：LONG_MAX、LONG_MIN

# GO语言

golang 的 math 包已经定义了以下常量：

Mathematical constants.

const (
    E   = 2.71828182845904523536028747135266249775724709369995957496696763 // https://oeis.org/A001113
    Pi  = 3.14159265358979323846264338327950288419716939937510582097494459 // https://oeis.org/A000796
    Phi = 1.61803398874989484820458683436563811772030917980576286213544862 // https://oeis.org/A001622

    Sqrt2   = 1.41421356237309504880168872420969807856967187537694807317667974 // https://oeis.org/A002193
    SqrtE   = 1.64872127070012814684865078781416357165377610071014801157507931 // https://oeis.org/A019774
    SqrtPi  = 1.77245385090551602729816748334114518279754945612238712821380779 // https://oeis.org/A002161
    SqrtPhi = 1.27201964951406896425242246173749149171560804184009624861664038 // https://oeis.org/A139339

    Ln2    = 0.693147180559945309417232121458176568075500134360255254120680009 // https://oeis.org/A002162
    Log2E  = 1 / Ln2
    Ln10   = 2.30258509299404568401799145468436420760110148862877297603332790 // https://oeis.org/A002392
    Log10E = 1 / Ln10
)

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Floating-point limit values. Max is the largest finite value representable by the type. SmallestNonzero is the smallest positive, non-zero value representable by the type.

const (
    MaxFloat32             = 3.40282346638528859811704183484516925440e+38  // 2**127 * (2**24 - 1) / 2**23
    SmallestNonzeroFloat32 = 1.401298464324817070923729583289916131280e-45 // 1 / 2**(127 - 1 + 23)

    MaxFloat64             = 1.797693134862315708145274237317043567981e+308 // 2**1023 * (2**53 - 1) / 2**52
    SmallestNonzeroFloat64 = 4.940656458412465441765687928682213723651e-324 // 1 / 2**(1023 - 1 + 52)
)

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Integer limit values.

const (
    MaxInt8   = 1<<7 - 1
    MinInt8   = -1 << 7
    MaxInt16  = 1<<15 - 1
    MinInt16  = -1 << 15
    MaxInt32  = 1<<31 - 1
    MinInt32  = -1 << 31
    MaxInt64  = 1<<63 - 1
    MinInt64  = -1 << 63
    MaxUint8  = 1<<8 - 1
    MaxUint16 = 1<<16 - 1
    MaxUint32 = 1<<32 - 1
    MaxUint64 = 1<<64 - 1
)

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自定义

golang的标准库里没有定义这些变量。不过可以用位操作运算，轻松定义这些常量。

无符号整型uint
- 其最小值是0，其二进制表示的所有位都为0，
```
const UINT_MIN uint = 0
```
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- 其最大值的二进制表示的所有位都为1，那么，
```
const UINT_MAX = ^uint(0)
```
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有符号整型int
- 根据补码，其最小值二进制表示，首位1，其余0，那么，
```
const INT_MIN = ^INT_MAX
```
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- 根据补码，其最大值二进制表示，首位0，其余1，那么，
```
const INT_MAX = int(^uint(0) >> 1)
```
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# Python

math库
```
math.inf
```
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浮点正无穷大。（对于负无穷大，使用 -math.inf 。）相当于 float('inf') 的输出。
'inf'
- 无穷大：float('inf')
- 无穷小：float('-inf')

上次更新: 2024/05/29, 06:25:22

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