samer@0: function d=subsampdata(a,b,varargin)
samer@0: % subsampdata - Use arbitrary function to test and filter elements of another sequence
samer@0: %
samer@0: % subsampdata :: 
samer@0: %	 natural		~ sample rate, 
samer@0: %	 data(A),	~ source data,
samer@0: %   ...    	~ options) 
samer@0: %	-> data(A).
samer@0: %
samer@0: % Options
samer@0: %	'datafn'::   	Data A->A	~ override function to get data
samer@0: % 	'stringfn'::	Data A->String	~ override conversion to string
samer@0: %	'nextfn'::  	Data A->(Data A | []) ~ override next function
samer@0: %
samer@0: % Methods
samer@0: %
samer@0: %   source :: filterdata(A) -> data(A).
samer@0: 
samer@0: if nargin==0, a=subsampdata(1,singleton(0)); end
samer@0: if isa(a,'subsampdata'), d=a;
samer@0: else
samer@0: 	d.n=a; 	
samer@0: 		
samer@0: 	opts=prefs('datafn',@datafn,'stringfn',@stringfn,'sizecheck',0,varargin{:});
samer@0: 	opts.nextfn=@nextfn;
samer@0: 	d=class(d,'subsampdata',ddata(b,size(b),opts));
samer@0: end
samer@0: 
samer@0: function x=datafn(d), x=head(source(d));
samer@0: function s=stringfn(d), s=sprintf('subsamp(%d)',tostring(d.n));
samer@0: function o=nextfn(o)
samer@0: 	for i=1:o.n
samer@0: 		o=next_c(o);
samer@0: 		if isempty(o), break; end
samer@0: 	end
samer@0: 
samer@0: 	
samer@0: