samer@36: % selector - Use boolean function to keep only matching elements from sequence
samer@3: %
samer@36: % selector :: (A->bool), seq(A) -> seq(A).
samer@36: classdef selector < seq
samer@3: 	properties (GetAccess=private, SetAccess=private)
samer@23: 		fn       % :: A->bool
samer@23: 		source   % :: seq(A)
samer@23: 		x        % :: A
samer@23: 	end
samer@23: 	methods (Static)
samer@23: 		function o=make(fn,source)
samer@23: 			source=dropwhile(inverse(fn),source);
samer@38: 			if isempty(source), o=nil; else o=seq.selector(fn,source); end
samer@23: 		end
samer@3: 	end
samer@3: 	methods
samer@36: 		function d=selector(fn,source)
samer@23: 			d.fn=fn; 	
samer@23: 			d.x=head(source);
samer@3: 			d.source=source;
samer@3: 		end
samer@3: 
samer@3: 		function z=elsize(o), z=elsize(d.x); end
samer@3: 		function s=tostring(o), s=sprintf('%s >> %s?',tostring(o.source),tostring(o.fn)); end
samer@3: 		function x=head(d), x=d.x; end
samer@3: 		function o=next(o)
samer@3: 			while 1
samer@3: 				o.source=next(o.source);
samer@23: 				if isempty(o.source), o=nil; return; end
samer@3: 				o.x=head(o.source);
samer@3: 				if o.fn(o.x), break; end
samer@3: 			end
samer@3: 		end
samer@3: 	end
samer@3: end
samer@23: 
samer@23: function g=inverse(f), g=@(x)~f(x); end