samer@4: function y=fixpoint(f,x0,varargin)
samer@4: % fixpoint - Find the fixed point of a function by repeated evaluation
samer@4: %
samer@4: % fixpoint :: 
samer@4: %    (A->A)	~'function to iterate',
samer@4: %    A      ~'initial value',
samer@4: %    options {
samer@4: %       its    :: natural/inf ~'maximimum numbert of iterations';
samer@4: %       testfn :: (A,A->boolean) ~'convergence test'
samer@4: %    }
samer@4: % -> maybe A ~'final value or nan if none'.
samer@4: 
samer@4: 
samer@37: opts=options('its',inf,'testfn',@epseq,varargin{:});
samer@4: 
samer@4: conv=opts.testfn;
samer@4: its =opts.its; 
samer@4: i=0; while i<its
samer@4: 	x=f(x0);
samer@4: 	if conv(x0,x), break; end
samer@4: 	x0=x; i=i+1;
samer@4: end
samer@4: 
samer@4: if i<its, y=x; else y=nan; end
samer@4: 
samer@4: function b=epseq(x,y), b=abs(y-x)<=eps(x);