 2019-02-16 19:07

# Go中的元组分配

Using this code:

``````for i := uint64(3); n > 1; i, n = i+2, n-1 {
``````

The Go Playground output is:

``````1999993
``````

Which is not correct result.

And this code:

``````func (p *Prime) Generate(n uint) {
p.Primes = make([]uint64, 1, n)
p.Primes = 2
next:
for i := uint64(3); n > 1; i += 2 {
q := uint64(math.Sqrt(float64(i)))
for _, v := range p.Primes[1:] {
if v > q {
break
}
if i%v == 0 {
continue next
}
}
p.Primes = append(p.Primes, i)
n--
}
}
``````

Which uses :

``````for i := uint64(3); n > 1; i += 2 {
``````

then

``````n--
``````

The output is correct:

``````15485863
``````

`go version go1.11.5 linux/amd64`

Am I missing something on tuple Assignments in Go?

• 写回答
• 关注问题
• 收藏
• 邀请回答

#### 1条回答默认 最新

• doushanlv5184 2019-02-16 19:21
已采纳

Nope, it is not tuple assignment that gives wrong result.

There is a subtle difference between the two code, which causes the bug. In the playgound code, `i,n = i+2,n-1` makes `n = n-1` runs everytimes the loop is iterated, while the github code only runs `n = n-1` when `i` is a prime (it skips `n--` if `continue next` runs).

打赏 评论