following simulates some functionality
package main
import (
"fmt"
"io"
"log"
"os"
)
func GOTO(f *os.File, e error) (*os.File, error) { return f, e }
func COPYGOTO(i int64, e error) (int64, error) { return i, e }
var err error
var r, w *os.File
func main() {
log.Println(Experimental("test.txt", "text.txt"))
}
func Experimental(src, dst string) error {
//goto jumps to "label" if present; selects values right to left; is
ignored with value´s zero value
r, err = GOTO(os.Open(src))
if err != nil {
goto err
}
defer r.Close()
w, err = GOTO(os.Create(dst))
if err != nil {
goto err
}
defer w.Close()
_, err = COPYGOTO(io.Copy(w, r))
if err != nil {
goto err
}
err = w.Close()
if err != nil {
goto err
}
return nil
err:
defer os.Remove(dst)
return fmt.Errorf("copy %s %s: %v", src, dst, err)
}
Matthias Mädel schrieb am Donnerstag, 14. April 2022 um 11:05:15 UTC+2:
> some refining...
>
> func Experimental(src, dst string) error {
>
> //goto jumps to "label" if present; selects values right to left; is
> ignored with value´s zero value
> goto r, err := os.Open(src)
> defer r.Close()
> goto w, err := os.Create(dst)
> defer w.Close()
> goto v, err := io.Copy(w, r)
> goto err := w.Close()
>
> //new: a "label" is a block also holding pointer to the actual value
> v: {
> //do something with value here...
> //return error
> }
>
> err:{
> defer os.Remove(dst)
> return fmt.Errorf("copy %s %s: %v", src, dst, err)
> }
>
> return nil
>
> }
>
> Ian Lance Taylor schrieb am Donnerstag, 14. April 2022 um 00:04:22 UTC+2:
>
>> On Wed, Apr 13, 2022 at 2:44 PM Matthias Mädel
>> <medienwer...@gmail.com> wrote:
>> >
>> > Please some advice if something like the following could be helpful and
>> if it is possible to implement with the compiler.
>> >
>> > Thank You
>> >
>> > func Experimental(src, dst string) error {
>> >
>> > //goto is blocked with err == nil
>> > goto r, err := os.Open(src)
>> > defer r.Close()
>> > goto w, err := os.Create(dst)
>> > goto v, err := io.Copy(w, r)
>> > goto err := w.Close()
>> > return nil
>> >
>> > //alternative
>> > goto err {
>> > r, err := os.Open(src)
>> > defer r.Close()
>> > w, err := os.Create(dst)
>> > v, err := io.Copy(w, r)
>> > err := w.Close()
>> > return nil
>> > }
>> >
>> > return err:
>> > w.Close()
>> > os.Remove(dst)
>> > fmt.Errorf("copy %s %s: %v", src, dst, err)
>>
>> Has some similarities to
>>
>> https://go.dev/issue/32611
>> https://go.dev/issue/34140
>> https://go.dev/issue/37035
>>
>> Ian
>>
>
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