如何找出切片中的元素位置？

How does one determine the position of an element present in slice?

I need something like the following:

type intSlice []int

func (slice intSlice) pos(value int) int {
    for p, v := range slice {
        if (v == value) {
            return p
        }
    }
    return -1
}

Sorry, there's no generic library function to do this. Go doesn't have a straight forward way of writing a function that can operate on any slice.

Your function works, although it would be a little better if you wrote it using range.

If you happen to have a byte slice, there is bytes.IndexByte.

Another option is to sort the slice using the sort package, then search for the thing you are looking for:

package main

import (
    "sort"
    "log"
    )

var ints = [...]int{74, 59, 238, -784, 9845, 959, 905, 0, 0, 42, 7586, -5467984, 7586}

func main() {
        data := ints
        a := sort.IntSlice(data[0:])
        sort.Sort(a)
        pos := sort.SearchInts(a, -784)
        log.Println("Sorted: ", a)
        log.Println("Found at index ", pos)
}

prints

2009/11/10 23:00:00 Sorted:  [-5467984 -784 0 0 42 59 74 238 905 959 7586 7586 9845]
2009/11/10 23:00:00 Found at index  1

This works for the basic types and you can always implement the sort interface for your own type if you need to work on a slice of other things. See http://golang.org/pkg/sort

Depends on what you are doing though.

There is no library function for that. You have to code by your own.

You can create generic function in idiomatic go way:

func SliceIndex(limit int, predicate func(i int) bool) int {
    for i := 0; i < limit; i++ {
        if predicate(i) {
            return i
        }
    }
    return -1
}

And usage:

xs := []int{2, 4, 6, 8}
ys := []string{"C", "B", "K", "A"}
fmt.Println(
    SliceIndex(len(xs), func(i int) bool { return xs[i] == 5 }),
    SliceIndex(len(xs), func(i int) bool { return xs[i] == 6 }),
    SliceIndex(len(ys), func(i int) bool { return ys[i] == "Z" }),
    SliceIndex(len(ys), func(i int) bool { return ys[i] == "A" }))

You could write a function;

func indexOf(element string, data []string) (int) {
   for k, v := range data {
       if element == v {
           return k
       }
   }
   return -1    //not found.
}

This returns the index of a character/string if it matches the element. If its not found, returns a -1.

func index(slice []string, item string) int {
    for i, _ := range slice {
        if slice[i] == item {
            return i
        }
    }
    return -1
}