为什么字节转换不一致golang？

概述我有以下示例,取自Addison-Wesley Golang一书,我稍作修改： package mainimport "fmt"// pc[i] is the population count of i.var pc [256]bytefunc init() { for i := range pc { pc[i] = pc[i/2] + byte(i&1) 我有以下示例,取自Addison-Wesley Golang一书,我稍作修改：

package mainimport "fmt"// pc[i] is the population count of i.var pc [256]bytefunc init() {    for i := range pc {        pc[i] = pc[i/2] + byte(i&1)    }}// PopCount returns the population count (number of set bits) of x.func PopCount(x uint64) int {    fmt.Printf("Value is %d\n",x)    fmt.Printf("byte(%d>>(0*8)) is %d\n",x,byte(x>>(0*8)))    y := byte(x>>(0*8))    return int(pc[y] +        pc[byte(x>>(1*8))] +        pc[byte(x>>(2*8))] +        pc[byte(x>>(3*8))] +        pc[byte(x>>(4*8))] +        pc[byte(x>>(5*8))] +        pc[byte(x>>(6*8))] +        pc[byte(x>>(7*8))])}func main() {    // fmt.Println(byte(256>>(0*8)))  // This blows up,but doesn't blow up on line 19 or line 20,why?    fmt.Println(PopCount(256))}

这是 *** 场上的相同代码：example-code
如果链接过期,这里是 *** 场,您可以粘贴上面的内容并播放：go playground

如果你取消注释

// fmt.Println(byte(256>>(0*8)))

你收到一个错误：

prog.go:31: constant 256 overflows byte

鉴于这是在PopCount中完成而不会爆炸,我不明白发生了什么.当有人在主要但不是在PopCount函数中执行此 *** 作时,有人可以帮助解释为什么它会爆炸吗？

我敢说我错过了一些明显的东西！

解决方法 这是因为256>>(0 * 8)(相当于256),是一个无类型常量,它太大而不适合一个字节 language spec状态中的规则

A constant value x can be converted to type T in any of these cases:

x is representable by a value of type T. x is a floating-point
constant,T is a floating-point type,and x is representable by a
value of type T after rounding using IEEE 754 round-to-even rules,but
with an IEEE -0.0 further rounded to an unsigned 0.0. The constant
T(x) is the rounded value. x is an integer constant and T is a string
type. The same rule as for non-constant x applIEs in this case.

在PopCount函数中,256值的类型为uint64,可以将其转换为字节,将其截断为0.

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