/*
 *  call-seq:
 *     dtable.as_exponent_of(number)                ->  a_dtable
 *     dtable.as_exponent_of(other)                 ->  a_dtable
 *  
 *  When argument is a number, this operation returns a copy of _dtable_ with each entry x replaced by _number_ ** x.
 *  When argument is a data array, this operation returns a copy of _dtable_ with each entry x replaced
 *  by the corresponding entry in the _other_ data array raised to the power x.
 */ VALUE dtable_as_exponent_of(VALUE ary, VALUE arg) {