Write a function that takes one double input value and returns only the repeating decimal, if any, as a string. Only decimals for which all digits are part of the repeating pattern will be counted. (See the 3rd example below.) Inputs will be in the range [0 1].

If no repeating decimal is found, the function should return an empty string. Of course the repeating decimal may break down in the last bit due to floating point arithmetic, but we will ignore that.

Examples:

T = repeatingdec(7/11)  % Returns T = '63'
T = repeatingdec(1/3)   % Returns T = '3'
T = repeatingdec(5/6)    % Returns T = ''
T = repeatingdec(0)      % Returns T = '0'