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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