巡回赛＃23：收益怪异的行为

Question

A Tour of Go #23:

package main

import (
    "fmt"
    "math"
)

func pow(x, n, lim float64) float64 {
    if v := math.Pow(x, n); v < lim {
        return v

    } else {
        fmt.Printf("%g >= %g
", v, lim)
    }
    // can't use v here, though
    return lim
}

func main() {
    fmt.Println(
        pow(3, 2, 10),
        pow(3, 3, 20),
    )
}

The results are:

27 >= 20
9 20

If I comment out the return v line, the results are:

27 >= 20
10 20

Why exactly does this happen? Why are results of the first pow() call not equal to 27 >= 20 and 10?

Answer 1

As already answered by @larsmans, you're passing a limit of 10 to the first call, thus the returned number is 10 instead of 20.

Change it to

func main() {
    fmt.Println(
        pow(3, 2, 20),
        pow(3, 3, 20),
    )
}

And you will see the following output when removing the return v line:

27 >= 20
20 20