Golang returning functions

kunrazor Published at

kunrazor :

Can anyone explain why 0's and 1's are printed and not anything else? Thank you!

func makeFunction(name string) func() {
    fmt.Println("00000")
    return func() {
        makeFunction2("abcef")
    }
}

func makeFunction2(name string) func() {
    fmt.Println("11111")
    return func() {
        makeFunction3("safsf")
    }
}

func makeFunction3(name string) func() {
    fmt.Println("33333")
    return func() {
        fmt.Printf("444444")
    }
}

func main() {
    f := makeFunction("hellooo")
    f()
}

Can anyone explain why 0's and 1's are printed and not anything else? Thank you!

Pierre Prinetti :

Let's look at your main:

Line 1

f := makeFunction("hellooo")

Side effect: printing "00000"
Return value: an anonymous function that executes makeFunction2("abcef"), assigned to the identifier f

Line 2

f()

which is equivalent to:

_ = f()

Side effect: printing "11111"
Return value: an anonymous function that executes makeFunction3("safsf"), discarded (you are not assigning the return value of f()).

makeFunction3 is never assigned to any identifier, and never called.

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