Go编程语言中的For循环

Question

I am writing a function to reverse a string using Go.

func main() {
        s := "abcde"
        r := []rune(s)
        for i, j := 0, len(s)-1; i < j; i, j = i++, j-- {
               r[i], r[j] = r[j], r[i]
        }
    fmt.Printf("%s
", string(r))
}

However, the compiler complaints about i, j = i++, j--, says, syntax error: unexpected ++, expecting {.

This function works if i change that into i, j = i+1, j-1. I don't know why this isn't allowed. Anyone can help? Thank u.

Answer 1

In Go, x-- and x++ are statements, not expressions, so you can't assign them like that, and it's by design.

The Spec says:

Unary operators have the highest precedence. As the ++ and -- operators form statements, not expressions, they fall outside the operator hierarchy. As a consequence, statement *p++ is the same as (*p)++.