What's the advantage of "If with a short statement"

Question

What's the advantage of using an "If with a short statement" in go lang. ref: go tour

if v := math.Pow(x, n); v < lim {
    return v
}

Instead of just write the statement before the if.

v := math.Pow(x, n)
if v < lim {
    return v
}

Answer 1

if v := math.Pow(x, n); v < lim is interesting if you don't need 'v' outside of the scope of 'if'.

It is mentioned in "Effective Go"

Since if and switch accept an initialization statement, it's common to see one used to set up a local variable.

if err := file.Chmod(0664); err != nil {
    log.Print(err)
    return err
}

The second form allows for 'v' to be used after the if clause.

The true difference is in the scope where you need this variable: defining it within the if clause allows to keep the scope where that variable is used to a minimum.