On 1 August 2017 at 13:57, Josh Humphries <jh...@bluegosling.com> wrote: > Although that solution creates a heap-allocated tmp for every element in the > slice. Using an interface, the value will be inlined instead of > heap-allocated if it fits without boxing (so most primitive types and > pointer types won't need heap allocation).
As it happens, it's the other way round - the solution using Interface can make an allocation per element, but the solution using Value does not. https://play.golang.org/p/Q0VHbfL7Ij Additionally, the solution using Interface can lose the type information in some cases and panic as a result. https://play.golang.org/p/WocF9CaPoR cheers, rog. > > ---- > Josh Humphries > jh...@bluegosling.com > > On Tue, Aug 1, 2017 at 7:29 AM, roger peppe <rogpe...@gmail.com> wrote: >> >> FWIW, you don't have to use Interface to do the swap: >> >> https://play.golang.org/p/O8lGJGGOXP >> >> On 31 July 2017 at 15:18, eZio Pan <eziopa...@gmail.com> wrote: >> > Hello, >> > I want to build a "universal slice reverser" with reflect.MakeFunc. But >> > I >> > don't know how to get a copy of reflect.Value's underlying value, which >> > make >> > result not correct. >> > >> > Here is the code: >> > >> > package main >> > >> > import ( >> > "fmt" >> > "reflect" >> > ) >> > >> > func reverse(in []reflect.Value) (out []reflect.Value) { >> > inls := in[0] >> > inlslen := inls.Len() >> > >> > for i, j := 0, inlslen-1; i < j; i, j = i+1, j-1 { >> > a := inls.Index(i) >> > b := inls.Index(j) >> > // how to get underlying value of a and b ? >> > a.Set(b) >> > b.Set(a) >> > } >> > return in >> > } >> > >> > var intFlipper func([]int) []int >> > >> > func main() { >> > emptyFunc := reflect.ValueOf(&intFlipper).Elem() >> > pseudoFunc := reflect.MakeFunc(emptyFunc.Type(), reverse) >> > emptyFunc.Set(pseudoFunc) >> > fmt.Printf("%v\n", intFlipper([]int{2, 3, 4, 5, 6, 7})) >> > } >> > >> > My code return [7 6 5 5 6 7], but excepting result is [7 6 5 4 3 2] >> > >> > -- >> > 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. >> >> -- >> 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. > > -- 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.
