/*
 *  call-seq:
 *     dvector.set(float)  -> dvector
 *     dvector.set(a_dvector)  -> dvector
 *  
 *  Modifies the entries of _dvector_ array.  If the argument is a float, then all of the
 *  entries are set to that value.  If the argument is another Dvector, then it must
 *  be the same length as _dvector_, and its contents are copied to _dvector_.
 */ VALUE dvector_set(VALUE ary, VALUE val) {