function a = or(a,b)% Compute the union of two regions.%% Syntax:%   "s3 = or(s1,s2)" or "s3 = s1 | s2"%% Description:%   Given two regions "s1" and "s2", the function returns the region "s3"%   which is the union of "s1" and "s2".%% Examples:%   * Suppose "s1 = region(5,[2 5])" and "s2 = region(5,[4])".%%   * "s3 = s1 | s2" returns a region "s3" containing states 2, 4, and 5.%% Implementation:%   Perform bit-wise OR operation between the look-up table from the two%   regions. The input regions must have the same number of states and%   same word size for the look-up table, otherwise, the function will%   issue an error message.%% See Also:%   region,set_state,isinregion,isuniverse,isempty,and,not% Check compatibility between two region objectsif (a.nstate == b.nstate) && (a.wordsize == b.wordsize)  N = a.nstate;  BIT_MAX = b.wordsize;  nword = ceil(N/BIT_MAX);  for idx = 1:nword    a.table(idx) = bitor(a.table(idx),b.table(idx));  end   elseif isempty(a)&& ~isempty(b)    a=b;elseif isempty(b)&& ~isempty(a)    % emptyelseif isempty(a)&&isempty(b)    a=region;else  error('Incompatible region objects given.')endreturn