On Thursday, October 20, 2016 at 10:34:41 PM UTC+8, T L wrote: > > > > On Thursday, October 20, 2016 at 9:58:46 PM UTC+8, T L wrote: >> >> >> >> 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 golang 1.7.1 doesn't release one copy of underlying data after > comparings: > > https://play.golang.org/p/Lu9FZ9iqn6 > https://play.golang.org/p/-wE2oUGce1 >
filed an issue: https://github.com/golang/go/issues/17526#issuecomment-255142005 and closed by the lighting issue closer. :) > > > >> >> 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.
