/*
 *  call-seq:
 *     dtable.safe_inv(cutoff=1e-99)   ->  a_dtable
 *  
 *  Returns a copy of _dtable_ with each entry x replaced by sign(x)/_cutoff_ if abs(x) < _cutoff_, 1/x otherwise.
 *     
 */ VALUE dtable_safe_inv(int argc, VALUE *argv, VALUE self) {