samer@0: function o=concat(sources,varargin)
samer@0: % concat - Concatenate sequences
samer@0: %
samer@0: % concat ::
samer@0: %    seq (seq A)	~ 'sequence of sequences'
samer@0: % -> seq A       ~ 'resultant sequence'.
samer@0: %
samer@0: % concat ::
samer@0: %    {[N]->seq A}	~ 'cell array of N data objects',
samer@0: % -> seq A          ~ 'resultant sequence'.
samer@0: 
samer@0: 
samer@0: if nargin==0, o=concat(repeat(0));
samer@0: elseif nargin==1 && isa(sources,'concat'), o=elems;
samer@0: else
samer@0: 	if iscell(sources), sources=celldata(sources); end
samer@0: 	if isempty(sources), o=[]; return; end
samer@0: 
samer@0: 	hd=head(sources);
samer@0: 	while isempty(hd)
samer@0: 		sources=next(sources);
samer@0: 		if isempty(sources), o=[]; return; end
samer@0: 		hd=head(sources);
samer@0: 	end
samer@0: 	o.current=hd;
samer@0: 	o.sources=next(sources);
samer@0: 	ft.datafn=@datafn;
samer@0: 	ft.charfn=@stringfn;
samer@0: 	ft.nextfn=@nextfn;
samer@0: 
samer@0: 	o=class(o,'concat',data(size(o.current),ft));
samer@0: end
samer@0: 
samer@0: 
samer@0: function x=datafn(o), x=head(o.current);
samer@0: function s=stringfn(o), s=sprintf('concat(%s|...)',tostring(o.current));
samer@0: function o=nextfn(o),
samer@0: 	s1=next(o.current);
samer@0: 	if ~isempty(s1), 
samer@0: 		o.current=s1; 
samer@0: 		o=setsize(o,size(o.current)); 
samer@0: 	else
samer@0: 		if isempty(o.sources), o=[]; return; end
samer@0: 
samer@0: 		hd=head(o.sources);
samer@0: 		while isempty(hd)
samer@0: 			o.sources=next(o.sources);
samer@0: 			if isempty(o.sources), o=[]; return; end
samer@0: 			hd=head(o.sources);
samer@0: 		end
samer@0: 		o.current=hd;
samer@0: 		o.sources=next(o.sources);
samer@0: 		o=setsize(o,size(hd)); 
samer@0: 	end