I like Alan's "useful definition" of a semantically reference type, which involves shared mutable state.
About the string type, I also like the implementation detail that var string t = s is O(1) in memory and running time, i.e. it happens internally to "copy the reference, not the bytes" : see https://play.golang.org/p/p-PD_yOnw6 It usually doesn't make much of a difference because most strings are short, and also they are not the best data structure to manipulate data (unlike []byte). But I take this implementation detail into account when I want to optimize code, especially to reduce the need for memory allocation. On Wednesday, October 19, 2016 at 6:44:26 PM UTC+2, adon...@google.com wrote: > > > 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. > > > -- 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. For more options, visit https://groups.google.com/d/optout.
