Re: [go-nuts] Expanding variables and fmt.Printf() issue
[pedantic correction]
* Marvin Renich [200629 14:10]:
> The final argument to Printf is []interface{}, while you are trying to
^
...interface{}
...Marvin
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Re: [go-nuts] Expanding variables and fmt.Printf() issue
* yves baumes [200629 03:22]:
> Hello,
>
> considering this code
>
> ```
> package main
>
> import (
> "fmt"
> )
>
> func main() {
> host := []string{"127", "0", "0", "1"}
>
> fmt.Printf("%v.%v.%v.%v\n", host[0], host[1], host[2], host[3])
> fmt.Printf("%v.%v.%v.%v\n", host[0:4]...)
> }
> ```
>
> The first Printf works and prints the host value.
> While the second one does not compile : "./args.go:11:34: cannot use
> host[0:4] (type []string) as type []interface {} in argument to fmt.Printf"
>
> If I use append() instead of Printf(), this expanding of the host variables
> just works out. Is this a compiler bug in the case of the fmt.Printf() ?
>From the language spec at
https://golang.org/ref/spec#Passing_arguments_to_..._parameters:
If the final argument is assignable to a slice type []T, it is
passed unchanged as the value for a ...T parameter if the argument
is followed by In this case no new slice is created.
The final argument to Printf is []interface{}, while you are trying to
pass []string. In order for this to work, []string would have to be
assignable to []interface{}, which it isn't.
This is related to a FAQ at
https://golang.org/doc/faq#convert_slice_of_interface.
If, after reading the above links and the definition of assignability at
https://golang.org/ref/spec#Assignability, you are still unclear why it
is not compiling, ask on the list for more help.
...Marvin
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Re: [go-nuts] Expanding variables and fmt.Printf() issue
On Mon, Jun 29, 2020 at 9:22 AM yves baumes wrote: > If I use append() instead of Printf(), this expanding of the host variables > just works out. Is this a compiler bug in the case of the fmt.Printf() ? No bug. That's how variable arguments and assignability rules are specified to work. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAA40n-WgLHeUhyEYtmVu1B1zeHByxm%2Ba5JyCqVhVU1VnAtddgA%40mail.gmail.com.
[go-nuts] Expanding variables and fmt.Printf() issue
Hello,
considering this code
```
package main
import (
"fmt"
)
func main() {
host := []string{"127", "0", "0", "1"}
fmt.Printf("%v.%v.%v.%v\n", host[0], host[1], host[2], host[3])
fmt.Printf("%v.%v.%v.%v\n", host[0:4]...)
}
```
The first Printf works and prints the host value.
While the second one does not compile : "./args.go:11:34: cannot use
host[0:4] (type []string) as type []interface {} in argument to fmt.Printf"
If I use append() instead of Printf(), this expanding of the host variables
just works out. Is this a compiler bug in the case of the fmt.Printf() ?
Regards
Yves.
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