更好地比较片或字节？

Question

I'm just curious on which of these methods is better (or if there's an even better one that I'm missing). I'm trying to determine if the first letter and last letter of a word are the same, and there are two obvious solutions to me.

if word[:1] == word[len(word)-1:]

or

if word[0] == word[len(word)-1]

As I understand it, the first is just pulling slices of the string and doing a string comparison, while the second is pulling the character from either end and comparing as bytes.

I'm curious if there's a performance difference between the two, and if there's any "preferable" way to do this?

Answer 1

If by letter you mean rune, then use:

func eqRune(s string) bool {
    if s == "" {
        return false // or true if that makes more sense for the app
    }
    f, _ := utf8.DecodeRuneInString(s)  // 2nd return value is rune size. ignore it.
    l, _ := utf8.DecodeLastRuneInString(s) // 2nd return value is rune size. ignore it.
    if f != l {
        return false
    }
    if f == unicode.ReplacementChar {
        // First and last are invalid UTF-8. Fallback to 
        // comparing bytes.
        return s[0] == s[len(s)-1]
    }
    return true
}

If you mean byte, then use:

func eqByte(s string) bool {
    if s == "" {
        return false // or true if that makes more sense for the app
    }
    return s[0] == s[len(s)-1]
}

Comparing individual bytes is faster than comparing string slices as shown by the benchmark in another answer.

playground example