如何为无符号整数类型指定可表示的最大值?

我想知道如何在下面的循环中初始化min,迭代计算一些结构的min和max长度。

var minLen uint = ???
var maxLen uint = 0
for _, thing := range sliceOfThings {
  if minLen > thing.n { minLen = thing.n }
  if maxLen < thing.n { maxLen = thing.n }
}
if minLen > maxLen {
  // If there are no values, clamp min at 0 so that min <= max.
  minLen = 0
}

使第一次通过比较,minLen >= n。


当前回答

我将使用math包来获取整数的最大值和最小值:

package main

import (
    "fmt"
    "math"
)

func main() {
    // integer max
    fmt.Printf("max int64   = %+v\n", math.MaxInt64)
    fmt.Printf("max int32   = %+v\n", math.MaxInt32)
    fmt.Printf("max int16   = %+v\n", math.MaxInt16)

    // integer min
    fmt.Printf("min int64   = %+v\n", math.MinInt64)
    fmt.Printf("min int32   = %+v\n", math.MinInt32)

    fmt.Printf("max float64 = %+v\n", math.MaxFloat64)
    fmt.Printf("max float32 = %+v\n", math.MaxFloat32)

    // etc you can see more int the `math`package
}

输出:

max int64   = 9223372036854775807
max int32   = 2147483647
max int16   = 32767
min int64   = -9223372036854775808
min int32   = -2147483648
max float64 = 1.7976931348623157e+308
max float32 = 3.4028234663852886e+38

其他回答

https://groups.google.com/group/golang-nuts/msg/71c307e4d73024ce?pli=1

相关部分:

由于整数类型使用二补运算,因此可以推断 int和uint的最小/最大常量值。例如, const maxint = ^uint(0) const MinUint = 0 const MaxInt = int(MaxInt >> 1) const MinInt = - maxint - 1

根据@CarelZA的评论:

uint8  : 0 to 255 
uint16 : 0 to 65535 
uint32 : 0 to 4294967295 
uint64 : 0 to 18446744073709551615 
int8   : -128 to 127 
int16  : -32768 to 32767 
int32  : -2147483648 to 2147483647 
int64  : -9223372036854775808 to 9223372036854775807

https://golang.org/ref/spec#Numeric_types为物理类型限制。

最大值是在math包中定义的,在你的例子中是math。MaxUint32

注意,因为没有溢出-超过最大值的增量会导致环绕。

我一直记得的方法是,取比特(int8是8位,int是 32位),除以8,你得到字节(int8将是一个字节,int 应该是四个字节)。

每个字节都是0xFF(有符号整数除外,在这种情况下是最有效的 字节将是0x7F)。结果如下:

package main

func main() {
   {
      var n int8 = 0x7F
      println(n) // 127
   }
   {
      var n uint8 = 0xFF
      println(n) // 255
   }
   {
      var n int = 0x7FFF_FFFF
      println(n) // 2147483647
   }
   {
      var n uint = 0xFFFF_FFFF
      println(n) // 4294967295
   }
}

我将使用math包来获取整数的最大值和最小值:

package main

import (
    "fmt"
    "math"
)

func main() {
    // integer max
    fmt.Printf("max int64   = %+v\n", math.MaxInt64)
    fmt.Printf("max int32   = %+v\n", math.MaxInt32)
    fmt.Printf("max int16   = %+v\n", math.MaxInt16)

    // integer min
    fmt.Printf("min int64   = %+v\n", math.MinInt64)
    fmt.Printf("min int32   = %+v\n", math.MinInt32)

    fmt.Printf("max float64 = %+v\n", math.MaxFloat64)
    fmt.Printf("max float32 = %+v\n", math.MaxFloat32)

    // etc you can see more int the `math`package
}

输出:

max int64   = 9223372036854775807
max int32   = 2147483647
max int16   = 32767
min int64   = -9223372036854775808
min int32   = -2147483648
max float64 = 1.7976931348623157e+308
max float32 = 3.4028234663852886e+38
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