function newnode(t:SyntaxClass) :tree;
   var n :tree;
begin new(n); n^.tag := t; newnode := n
end;

function cons(h, t :tree) :tree;
   var c :tree;
begin c := newnode(list);
      c^.hd := h; c^.tl := t;
      cons := c
end;

function append( a, b :tree ) :tree;
begin if a=nil then append:=b else append:=cons(a^.hd, append(a^.tl, b))
end;

{\fB Tree Manipulation. \fP}