A dyadic rational is a rational number of the form with an integer and a nonnegative integer . Examples are , , zero and every integer. In lowest terms, its denominator is a power of two, so its magnitude has a finite binary expansion.
A positive dyadic rational also has a binary representation ending in infinitely many ones. Replacing the last nonzero binary digit by zero and filling all lower places with ones preserves the value, becauseFor example, . Zero has no second nonnegative expansion of this type. The same ambiguity applies to the magnitude of a negative dyadic rational, with its sign kept separately.
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