Re: veccount

[Karim Belabas <Karim.Belabas@math.u-bordeaux.fr>]

* Ruud H.G. van Tol [2022-12-24 18:16]:
> 
> Is there a more canonical way to do runlength-counting?
> 
> { my(count(v)=
> my(a=List(),c=1);for(i=1,#v-1,if(v[i+1]==v[i],c++,listput(a,c);c=1));Vec(a));
>   print(count([logint(2^i,3)|i<-[0..98]]));
> }
> [2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1,
> 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 2,
> 1, 2, 2, 1, 2, 1, 2, 1, 2, 2, 1]

? v = [logint(2^i,3)|i<-[0..98]]
%1 = [0, 0, 1, 1, 2, 3, 3, 4, 5, 5, 6, 6, 7, 8, 8, 9, 10, 10, 11, 11, 12, 13, 13, 14, 15, 15, 16, 17, 17, 18, 18, 19, 20, 20, 21, 22, 22, 23, 23, 24, 25, 25, 26, 27, 27, 28, 29, 29, 30, 30, 31, 32, 32, 33, 34, 34, 35, 35, 36, 37, 37, 38, 39, 39, 40, 41, 41, 42, 42, 43, 44, 44, 45, 46, 46, 47, 47, 48, 49, 49, 50, 51, 51, 52, 52, 53, 54, 54, 55, 56, 56, 57, 58, 58, 59, 59, 60, 61, 61]

? matreduce(v)~
%2 = 
[0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61]

[2 2 1 2 1 2 2 1 2 1 2 2 1 2 1 2 1 2 2 1 2 1 2 2 1 2 1 2 1 2 2 1 2 1 2 2 1 2 1 2 1 2 2 1 2 1 2 2 1 2 1 2 2 1 2 1 2 1 2 2 1 2]


Cheers,

    K.B.
--
Karim Belabas  /  U. Bordeaux,  vice-président en charge du Numérique
Institut de Mathématiques de Bordeaux UMR 5251 - (+33) 05 40 00 29 77
http://www.math.u-bordeaux.fr/~kbelabas/
`