For loop in Go programming language

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\n", 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.

OneOfOne · Accepted Answer · 2014-07-12 20:00:05Z

2

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)++.

answered Jul 12, 2014 at 20:00

OneOfOne

100k22 gold badges195 silver badges187 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

James Henstridge Over a year ago

Furthermore, in languages where they are expressions, i = i++ is a bit pointless: "increment i, and store the pre-increment value in i"?

Collectives™ on Stack Overflow

For loop in Go programming language

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related