On Thursday, October 20, 2016 at 7:31:25 PM UTC+8, Val wrote: > > 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. >
So, comparing two long same stings at the first time may spend much time? It looks strings are much like interfaces here: https://play.golang.org/p/fEzxkzLfS2 > > 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.
