英文:
variadic pack and unpack in go lang: '[]string{f(v)}...'
问题
我在浏览 GitHub 时找到了这个函数：
func Accumulate(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, []string{f(v)}...)
}
return result
}
这个方法可以简化为以下形式吗？还是我漏掉了什么？
func Accumulate(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, f(v))
}
return result
}
英文:
I found this function while browsing github:
func Accumulate(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, []string{f(v)}...)
}
return result
}
Could this method be simplified to the following, or am I missing something:
func Accumulate(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, f(v))
}
return result
}
答案1
得分: 1
你提供的代码是正确的，易于理解的。我写了一个基准测试：
package p
import (
"testing"
"strings"
)
var s = []string{"hello", "world", "this", "new", "world"}
func BenchmarkAcc1(b *testing.B) {
for n := 0; n < b.N; n++ {
Accumulate(s, strings.ToUpper)
}
}
func BenchmarkAcc2(b *testing.B) {
for n := 0; n < b.N; n++ {
Accumulate2(s, strings.ToUpper)
}
}
以下是我得到的一些结果：
% go test -benchtime=10s -bench=.
testing: warning: no tests to run
PASS
BenchmarkAcc1 10000000 1510 ns/op
BenchmarkAcc2 10000000 1492 ns/op
ok _/home/satran/test 33.064s
如你所见，实际上并没有性能提升，事实上你的版本效果更好。
以下是源代码：
package p
func Accumulate(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, []string{f(v)}...)
}
return result
}
func Accumulate2(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, f(v))
}
return result
}
希望对你有帮助！
英文:
The version you have written is correct and sane to understand. I wrote a benchmark:
package p
import (
"testing"
"strings"
)
var s = []string{"hello", "world", "this", "new", "world"}
func BenchmarkAcc1(b *testing.B) {
for n := 0; n < b.N; n++ {
Accumulate(s, strings.ToUpper)
}
}
func BenchmarkAcc2(b *testing.B) {
for n := 0; n < b.N; n++ {
Accumulate2(s, strings.ToUpper)
}
}
Here are a few results I got:
% go test -benchtime=10s -bench=.
testing: warning: no tests to run
PASS
BenchmarkAcc1 10000000 1510 ns/op
BenchmarkAcc2 10000000 1492 ns/op
ok _/home/satran/test 33.064s
As you can see there is no performance gain either, in fact your version works better.
Here is the source:
package p
func Accumulate(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, []string{f(v)}...)
}
return result
}
func Accumulate2(s []string, f func(st string) string) (result []string) {
for _, v := range s {
result = append(result, f(v))
}
return result
}
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