function s = binstr(x)

if ~finite(x)|(length(x)~=1), error('x must be a finite scalar.'), end
b = (x<0); x = abs(x);
s = zeros(1,53);
[f,e] = log2(x);
for i = 1:53
f = 2*f;
d = floor(f);
f = f - d;
s(i) = d+48;
end
s = ['0.' s sprintf('*2^(%d)',e)];
if b, s = ['-' s]; end
s = setstr(s);