On Thursday, October 20, 2016 at 4:46:52 PM UTC+8, Dave Cheney wrote:
>
> What is a pointer wrapper value?
>
struct {
p *T
}
>
> in all seriousness, if you review the git history of the Go spec you'll
> find the word "reference" was purged about two years ago, in effect, to try
> to stem these discussions.
>
Yes, I found many old docs and old web pages are still using the word
"reference value".
I think it is an unnecessary word. The concepts of values and pointer
values are sufficient to understand Golang values well.
>
> On Thursday, 20 October 2016 16:07:07 UTC+9, T L wrote:
>>
>>
>>
>> On Thursday, October 20, 2016 at 12:44:26 AM UTC+8, adon...@google.com
>> wrote:
>>>
>>> On Wednesday, 19 October 2016 06:33:09 UTC-4, Jan Mercl wrote:
>>>>
>>>> On Wed, Oct 19, 2016 at 12:27 PM T L <tapi...@gmail.com> wrote:
>>>>
>>>> Nothing. The language specification does not mention it.
>>>>
>>>> People use that term based on definitions specified for other
>>>> programming languages, but those are not always equal to each other.
>>>>
>>>
>>> Jan is write that the term does not appear in the spec, but I think it's
>>> possible to come up with a useful definition of a reference type that
>>> applies to all ALGOL-like languages: a reference type is one whose values
>>> indirectly refer to mutable state. So, pointers are obviously references,
>>> as are slices, maps, and channels. But a string is not a reference
>>> because, although internally it contains a pointer, you cannot mutate the
>>> array of bytes to which it refers. Functions may be references, because a
>>> closure may refer to lexically enclosing variables. Structs and arrays are
>>> references if their elements contain references. An interface value is a
>>> reference if its payload contains a references.
>>>
>>> The essence of a reference is that copying one creates a new alias for
>>> its underlying state, and changes made via one alias are visible to all
>>> others. This definition is not absolute: a pointer to an immutable data
>>> structure, for example, can be considered to have "value" (non-reference)
>>> semantics since although it points to a variable, that variable can never
>>> be changed.
>>>
>>>
>> So reference values must be pointer related? Reference values can be
>> direct pointer values or pointer wrapper values, people can modify the
>> values pointed by the pointers directly or indirectly (through the methods
>> or other mechanisms exposed on the reference value identifier)?
>>
>
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