Go中的惯用类型转换

问题描述：

I was playing around with Go and was wondering what the best way is to perform idiomatic type conversions in Go. Basically my problem lays within automatic type conversions between uint8, uint64, and float64. From my experience with other languages a multiplication of a uint8 with a uint64 will yield a uint64 value, but not so in go.

Here is an example that I build and I ask if this is the idiomatic way of writing this code or if I'm missing an important language construct.

package main

import ("math";"fmt")

const(Width=64)

func main() {

    var index uint32
    var bits uint8

    index = 100
    bits = 3

    var c uint64
    // This is the line of interest vvvv
    c = uint64(math.Ceil(float64(index * uint32(bits))/float64(Width)))
    fmt.Println("Test: %v
", c)
}

From my point of view the calculation of the ceiling value seems unnecessary complex because of all the explicit type conversions.

Thanks!

我正在玩Go，想知道在Go中执行惯用类型转换的最佳方法是什么。基本上，我的问题在于uint8 code>， uint64 code>和 float64 code>之间的自动类型转换。根据我在其他语言上的经验，将 uint8 code>与 uint64 code>相乘会产生一个 uint64 code>值，但实际上并非如此。 p >

这是我构建的一个示例，请问这是编写代码的惯用方式还是我缺少重要的语言构造？ p>


   package main 
 
import（“ math”;“ fmt”）
 
const（Width = 64）
 
func main（）{
 
 var index uint32 
 var bits uint8 
 \  n索引= 100 
位= 3 
 
 var c uint64 
 //这是感兴趣的行vvvv 
c = uint64（math.Ceil（float64（index * uint32（bits））/ float64（Width）  ））
 fmt.Println（“ Test：％v 
”，c）
} 
  code>  pre> 
 
 从我的角度来看，计算上限值 由于所有显式类型转换，似乎不必要的复杂性。   p> 
 
 
谢谢！ p> 
  div>

答

There are no implicit type conversions for non-constant values.

You can write

var x float64
x = 1

But you cannot write

var x float64
var y int

y = 1
x = y

See the spec for reference.

There's a good reason, to not allow automatic/implicit type conversions, as they can become very messy and one has to learn many rules to circumvent the various caveats that may occur. Take the Integer Conversion Rules in C for example.

答

For example,

package main

import "fmt"

func CeilUint(a, b uint64) uint64 {
    return (a + (b - 1)) / b
}

func main() {
    const Width = 64
    var index uint32 = 100
    var bits uint8 = 3
    var c uint64 = CeilUint(uint64(index)*uint64(bits), Width)
    fmt.Println("Test:", c)
}

Output:

Test: 5

Go中的惯用类型转换

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