samer@0: function o=takewhile(f,source)
samer@0: % takewhile - Take elements of seq while a condition is met.
samer@0: %
samer@0: % takewhile :: (A->bool), seq A -> seq A
samer@0: 
samer@0: if nargin==0, o=takewhile(@(e)true,0);
samer@0: elseif isa(source,'takewhile'), o=source;
samer@0: elseif isempty(source), o=[]; 
samer@0: elseif ~f(head(source)), o=[];
samer@0: else
samer@0: 	ft.datafn=@datafn;
samer@0: 	ft.stringfn=@stringfn;
samer@0: 	ft.nextfn=@nextfn;
samer@0: 	o.f=f;
samer@0: 	o.x=head(source);
samer@0: 	o=class(o,'takewhile',ddata(source,size(source),ft));
samer@0: end
samer@0: 
samer@0: function x=datafn(o), x=o.x;
samer@0: function s=stringfn(o), s=sprintf('takewhile(%s)',tostring(o.f));
samer@0: function o=nextfn(o)
samer@0: 	o=next_c(o);
samer@0: 	if ~isempty(o), 
samer@0: 		o.x=headsource(o);
samer@0: 		if ~o.f(o.x), o=[]; end
samer@0: 	end
samer@0: 
samer@0: 	
samer@0: