No, I'm saying that the current implementation is two pointers.
The value is addressed by the second pointer. So you cannot really put a
const in an interface. (thought experiment)
Of course, in the specific case of boxing a value type, that could work. If
you accept that the *typ never changes throughout the program.
The question is, why a special case, what would you use it for? sync.Pools ?
If it's just for error variables to be constants, maybe it is not worth it.
What problem does it solve ?
On Saturday, August 6, 2016 at 11:11:24 AM UTC+2, T L wrote:
>
>
>
> On Saturday, August 6, 2016 at 4:06:07 PM UTC+8, atd...@gmail.com wrote:
>>
>> Possibily, if you freeze the type of things that can be boxed by the
>> interface. But what would it be useful for ?
>> That would just mean that an interface is constant. Not even that the
>> value it wraps can't be changed (because with the current implementation,
>> the values an interface wraps need to be addressable).
>>
>
> you mean a value should be addressable to let an interface wraps wrap it?
> Not true, "_ = interface{}(1)" is valid in current implementation.
>
>
>>
>>
>>
>> On Saturday, August 6, 2016 at 9:53:26 AM UTC+2, T L wrote:
>>>
>>> Is it possible to make an interface constant if its concrete value type
>>> is bool/number/string?
>>>
>>> On Saturday, August 6, 2016 at 3:48:17 AM UTC+8, Ian Lance Taylor wrote:
>>>>
>>>> On Fri, Aug 5, 2016 at 11:21 AM, T L <tapi...@gmail.com> wrote:
>>>> >
>>>> > For an interface value, its internal values will never change.
>>>> > Are there any problems if golang supports constant interface values?
>>>>
>>>> Pedantically, in Go, constants are untyped by default. It doesn't
>>>> make sense to speak of an untyped interface value. I would describe
>>>> what you are asking for as an immutable variable. I've often thought
>>>> that immutable variables would be useful in Go, but since they have to
>>>> be initialized it's not that simple. For example, io.EOF is
>>>> initialized using a function call. That means that it can't actually
>>>> be in read-only memory, and of course it's possible to take it's
>>>> address. How do we prevent it from being changed, without introducing
>>>> an immutable qualifier into the type system? It's a complex problem
>>>> for which I have no solution. And the benefits of an immutable
>>>> variable aren't all that high.
>>>>
>>>> Ian
>>>>
>>>
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