假设你有以下三元表达式(C语言):

int a = test ? 1 : 2;

在Go中惯用的方法是简单地使用if块:

var a int

if test {
  a = 1
} else {
  a = 2
}

但是，这可能不符合您的要求。在我的例子中，我需要一个代码生成模板的内联表达式。

我使用了一个立即求值的匿名函数:

a := func() int { if test { return 1 } else { return 2 } }()

这确保了两个分支都不会被计算。

没有括号，map三元很容易读:

c := map[bool]int{true: 1, false: 0} [5 > 4]

No Go没有三元运算符。使用if/else语法是惯用的方法。

Why does Go not have the ?: operator? There is no ternary testing operation in Go. You may use the following to achieve the same result: if expr { n = trueVal } else { n = falseVal } The reason ?: is absent from Go is that the language's designers had seen the operation used too often to create impenetrably complex expressions. The if-else form, although longer, is unquestionably clearer. A language needs only one conditional control flow construct. — Frequently Asked Questions (FAQ) - The Go Programming Language

我已经编译了一些项目并比较了速度。

/*
go test ternary_op_test.go -v -bench="^BenchmarkTernaryOperator" -run=none -benchmem
*/
package _test

import (
    "testing"
)

func BenchmarkTernaryOperatorIfElse(b *testing.B) {
    for i := 0; i < b.N; i++ {
        if i%2 == 0 {
            _ = i
        } else {
            _ = -i
        }
    }
}

// https://stackoverflow.com/a/45886594/9935654
func Ternary(statement bool, a, b interface{}) interface{} {
    if statement {
        return a
    }
    return b
}

func BenchmarkTernaryOperatorTernaryFunc(b *testing.B) {
    for i := 0; i < b.N; i++ {
        _ = Ternary(i%2 == 0, i, -i).(int)
    }
}

// https://stackoverflow.com/a/34636594/9935654
func BenchmarkTernaryOperatorWithFunc(b *testing.B) {
    for i := 0; i < b.N; i++ {
        _ = func() int {
            if i%2 == 0 {
                return i
            } else {
                return -i
            }
        }
    }
}

// https://stackoverflow.com/a/31483763/9935654
func BenchmarkTernaryOperatorMap(b *testing.B) {
    for i := 0; i < b.N; i++ {
        _ = map[bool]int{true: i, false: -i}[i%2 == 0]
    }
}

输出

goos: windows
goarch: amd64
cpu: Intel(R) Core(TM) i7-8565U CPU @ 1.80GHz
BenchmarkTernaryOperatorIfElse
BenchmarkTernaryOperatorIfElse-8                1000000000               0.4460 ns/op          0 B/op          0 allocs/op
BenchmarkTernaryOperatorTernaryFunc
BenchmarkTernaryOperatorTernaryFunc-8           1000000000               0.3602 ns/op          0 B/op          0 allocs/op
BenchmarkTernaryOperatorWithFunc
BenchmarkTernaryOperatorWithFunc-8              659517496                1.642 ns/op           0 B/op          0 allocs/op
BenchmarkTernaryOperatorMap
BenchmarkTernaryOperatorMap-8                   13429532                82.48 ns/op            0 B/op          0 allocs/op
PASS
ok      command-line-arguments  4.365s

关于三元运算符的惯用方法，还有一个建议:

package main

import (
    "fmt"
)

func main() {
    val := -5

    index := func (test bool, n, d int) int {
        if test {
            return n
        }
        return d
    }(val > 0, val, -val)
    
    fmt.Println(index)
}

去操场

埃尔德的回答既有趣又有创意，甚至可以说很聪明。

但是，建议改为:

var index int
if val > 0 {
    index = printPositiveAndReturn(val)
} else {
    index = slowlyReturn(-val)  // or slowlyNegate(val)
}

是的，它们都编译成本质上相同的程序集，但是这段代码比调用匿名函数只返回一个可以首先写入变量的值要清晰得多。

基本上，简单清晰的代码比有创意的代码更好。

此外，任何使用map文字的代码都不是一个好主意，因为在Go中映射根本不是轻量级的。自Go 1.3以来，小型地图的随机迭代顺序得到了保证，为了加强这一点，小型地图的内存效率大大降低。

As a result, making and removing numerous small maps is both space-consuming and time-consuming. I had a piece of code that used a small map (two or three keys, are likely, but common use case was only one entry) But the code was dog slow. We're talking at least 3 orders of magnitude slower than the same code rewritten to use a dual slice key[index]=>data[index] map. And likely was more. As some operations that were previously taking a couple of minutes to run, started completing in milliseconds.\