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Matthias Mädel
Apr 13, 2022, 5:44:06 PM4/13/22
to golang-nuts
Hello
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)
}
Ian Lance Taylor
Apr 13, 2022, 6:04:22 PM4/13/22
to Matthias Mädel, golang-nuts
https://go.dev/issue/32611
https://go.dev/issue/34140
https://go.dev/issue/37035
Ian
Matthias Mädel
Apr 14, 2022, 5:05:15 AM4/14/22
to golang-nuts
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
}
Matthias Mädel
Apr 14, 2022, 12:15:35 PM4/14/22
to golang-nuts
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)
}
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