Thanks Axel, Now this makes sense to me.
All the best, Jochen On Friday, 18 March 2022 at 12:04:04 UTC axel.wa...@googlemail.com wrote: > https://go.dev/ref/spec#Length_and_capacity says: > >> The expression len(s) is constant if s is a string constant. The >> expressions len(s) and cap(s) are constants if the type of s is an array or >> pointer to an array and the expression s does not contain channel receives >> or (non-constant) function calls; in this case s is not evaluated. >> Otherwise, invocations of len and cap are not constant and s is evaluated. > > So, in your case, the array contains a function call, so `len(…)` is not > constant. > > Here is a case where the clause from the spec makes an observable > difference: https://go.dev/play/p/jeCk6vHzf9u > Without that clause, the range loop would have to iterate over the element > of the pointee, causing a nil-dereference panic. The clause allows this > code to work. > > On Fri, Mar 18, 2022 at 12:43 PM Jochen Voss <joche...@gmail.com> wrote: > >> Dear all, >> >> The spec at https://go.dev/ref/spec#For_range says >> >> "The range expression x is evaluated once before beginning the loop, with >> one exception: if at most one iteration variable is present and len(x) is >> constant, the range expression is not evaluated." >> >> What does the second half of this sentence mean? >> >> My guess was that this says that in "for i := range [3]int{1, 2, f()} >> ..." the function f is not called, but I quick experiment shows that this >> guess is wrong, see https://go.dev/play/p/MXqH_C7mllx . >> >> All the best, >> Jochen >> >> -- >> 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...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/db6d865e-233e-4120-8ce5-5feb832732b6n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/golang-nuts/db6d865e-233e-4120-8ce5-5feb832732b6n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/589d8a21-931c-4c74-95e8-62ef83a501a9n%40googlegroups.com.
