Hi Marc, My understanding is that ranges are pretty cheap to construct, and in any case, the range @x[0..*-1] is just the index of all elements in @x. The .grep() approach may be most useful if you have a function (e.g. %, %%, and .is-prime shown below):
> (0...9) (0 1 2 3 4 5 6 7 8 9) > (0...9)[0..*-1] (0 1 2 3 4 5 6 7 8 9) > (0...9)[(0..*-1).grep: * ] (0 1 2 3 4 5 6 7 8 9) > (0...9)[(0..*-1).grep: * %% 2 ] (0 2 4 6 8) > (0...9)[(0..*-1).grep: * % 2 ] (1 3 5 7 9) > (0...9)[(0..*-1).grep: *.is-prime ] (2 3 5 7) > You can find a related example in the docs ( https://docs.raku.org/routine/grep#class_HyperSeq). Anyway, I'm sure each approach has its fans, Best, Bill. On Tue, Aug 24, 2021 at 3:59 AM Marc Chantreux <e...@phear.org> wrote: > hello everyone, > > I made a mistake while replying to all of us so anwsers never reached > your boxes. I'll summerize in one answer: > > Bill: > > > Is it just even/odd elements that you want to separate out? If so, maybe > > .grep() is your friend here > > I don't think it is: 0, 2 ... * seems to be > > * closer to what i have in mind when i think about the problem > (so i invoke readability there) > * probably more efficient than (0..*).grep(* % 2) that > * generate twice the number of required elements > * need to filter the result > > Also, trying to play with this version: > > my ($a,$b) = > .[0,2...*], > .[1,3...*] > with <AaBbCc>.comb; > > just don't work because the lists are squashed into scalar context > in the process. > > So Brian and Fernando made my day with := and the unexpected power of > the [] operator. > > my (@a,@b) := <AaBbCc>.comb[ [0,2...*], [1,3...*] ]; > > I really like how declarative it is. Also the use of := now seems > obvious to me. > > Sigils still remains something strange to me desprite all your examples > but i'll take some time. thanks everyone. > > marc > >
