[Jprogramming] nubsieve modulo rotation

[olius at bluewin.ch]

> sig3 does not work:

Funny, it works ok on my copy of j807 (and is very fast, well done Mike).
It doesn't find the minimum rotation of a vector though, it directly takes a matrix and returns the nubsieve of the rows, so it expects a rank 2 argument.

> I compared my solution with sigb_LdF and sigi_Ldf of Louis de Forcrand and sig1_MD and sig2_MD of Mike Day.
> Obviously the special cases are easy to win, but they also revealed a bug in sigi_LdF.

Indeed a {. was missing on the last line:

sigi=: (|.~ 3 : 0)"1
 i=. i.#y
 for. y do.
  if. 1 = #i do. break. end.
  i=. i ((= <./)@:{ # [) y
  y=. 1|.y
 end.
 {.i
)

Without it, |. was receiving a vector of length n on the left and so was expecting its right argument to be of rank n (which never happened when n > 1).

Louis