extra/sequences/rotated/rotated.factor

   1 ! Copyright (C) 2012 John Benediktsson
   2 ! See http://factorcode.org/license.txt for BSD license
   3 USING: accessors kernel math sequences ;
   4 IN: sequences.rotated
   5
   6 TUPLE: rotated
   7 { seq read-only }
   8 { n integer read-only } ;
   9
  10 C: <rotated> rotated
  11
  12 M: rotated length seq>> length ;
  13
  14 M: rotated virtual@
  15     [ n>> + ] [ seq>> ] bi [
  16         length over 0 < [ + ] [
  17             2dup >= [ - ] [ drop ] if
  18         ] if
  19     ] keep ;
  20
  21 M: rotated virtual-exemplar seq>> ;
  22
  23 INSTANCE: rotated virtual-sequence
  24
  25 : all-rotations ( seq -- seq' )
  26     dup length <iota> [ <rotated> ] with map ;