tree insert( key, t )
     typekey key[K];
     tree t;
     { tree InsertIndx();
     return( InsertIndx(key,t,1) );
     }

     tree InsertIndx( key, t, lev )
     typekey key[K];
     tree t;
     int lev;

     { int i, indx;
       tree t1;
     if ( t == NULL ) return( NewDataNode(key) );
     if ( IsData(t) ) {
          for( i=0; i<K && key[i] == t->k[i]; i++ );
          if ( i >= K ) {
               Error /*** Key already in table ***/;
               return(t);
               }
          else  {   t1 = NewIntNode();
               indx = 0;
               for ( i=0; i<K; i++ ) indx = 2*indx + bit(lev,t->k[i]);
               t1->p[indx] = t;
               t = t1;
               }
          }
     indx = 0;
     for ( i=0; i<K; i++ ) indx = 2*indx + bit(lev,key[i]);
     t->p[indx] = InsertIndx( key, t->p[indx], lev+1 );
     return( t );
     };