proposal: strings: add ListIndex

[256dpi]

While reading the source code of many packages lately I stumbled a lot over the following function declaration:

func stringInList(list []string, str string) bool {
    for _, val := range list {
        if val == str {
            return true
        }
    }

    return false
}

I have the feeling that searching a slice of strings for the first occurrence of a string is a very common need and might be a good addition to the standard library.

I would propose the following function for the strings package:

func ListIndex(list []string, str string) int {
    for i, val := range list {
        if val == str {
            return i
        }
    }

    return -1
}

I know adding stuff to the standard library is a big thing, but I had to give it a least a try. ;)

[Ganners]

If you're happy for your list of strings to be sorted, then this essentially exists as sort.SearchStrings: https://golang.org/pkg/sort/#SearchStrings

The linear search listed above is so trivial in implementation that I wouldn't think it's worth adding, binary search is far superior if you can afford the sort.

[griesemer]

Adding this would set a precedent for many other little "useful" utility functions that are trivial to write. Where does it end? I'm against adding things like this to the std lib.

[256dpi]

@Ganners I wasn't aware of sort.SearchStrings existence... Thanks for pointing it out. You're right, a binary search would be a better choice.

@griesemer: I wouldn't ask for a Max(ints []int) int function, but as there is already a package with string utility functions in place, I thought it would be a nice addition. I scrolled multiple times through the package to check if there is really no such function already there. ;)