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// run -gcflags=-G=3
// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"fmt"
)
// Index returns the index of x in s, or -1 if not found.
func Index[T comparable](s []T, x T) int {
for i, v := range s {
// v and x are type T, which has the comparable
// constraint, so we can use == here.
if v == x {
return i
}
}
return -1
}
type obj struct {
x int
}
type obj2 struct {
x int8
y float64
}
type obj3 struct {
x int64
y int8
}
type inner struct {
y int64
z int32
}
type obj4 struct {
x int32
s inner
}
func main() {
want := 2
vec1 := []string{"ab", "cd", "ef"}
if got := Index(vec1, "ef"); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
vec2 := []byte{'c', '6', '@'}
if got := Index(vec2, '@'); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
vec3 := []*obj{&obj{2}, &obj{42}, &obj{1}}
if got := Index(vec3, vec3[2]); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
vec4 := []obj2{obj2{2, 3.0}, obj2{3, 4.0}, obj2{4, 5.0}}
if got := Index(vec4, vec4[2]); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
vec5 := []obj3{obj3{2, 3}, obj3{3, 4}, obj3{4, 5}}
if got := Index(vec5, vec5[2]); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
vec6 := []obj4{obj4{2, inner{3, 4}}, obj4{3, inner{4, 5}}, obj4{4, inner{5, 6}}}
if got := Index(vec6, vec6[2]); got != want {
panic(fmt.Sprintf("got %d, want %d", got, want))
}
}
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