ast_util.sa

Java写的词法/语法分析器。可生成JAVA语言或者是C++的词法和语法分析器。并可产生语法分析树和对该树进行遍历

(* 

  ANTLR Translator Generator
  Project led by Terence Parr at http://www.jGuru.com
  Software rights: http://www.antlr.org/RIGHTS.html
 
  $Id: //depot/code/org.antlr/release/antlr-2.7.0/lib/sather/Antlr/ast_util.sa#1 $

*)

class ANTLR_AST_UTIL{AST < $ANTLR_AST{AST}} is

   -- Duplicate tree including siblings of root. 
   dup_list( t : AST ) : AST is
      res : AST := dup_tree(t);  -- if void(t), then void(result)
      nt : AST := res;
      loop while! ( ~void(t) ); -- for each sibling of the root
	 t := t.next_sibling;
	 nt.next_sibling( dup_tree(t) ); -- dup each subtree, building new tree
	 nt := nt.next_sibling;
      end;
      return res;
   end;
   
   -- Duplicate a tree, assuming this is a root node of a tree --n
   -- duplicate that node and what's below; ignore siblings of root node.
   dup_tree( t : AST ) : AST is
      res : AST := t.dup;  -- make copy of root
      -- copy all children of root.
      if ( ~void(t) ) then
	 res.first_child( dup_list( t.first_child ) );
      end;
      return res;
   end;

   -- Make a tree from a list of nodes.  The first element in the
   -- array is the root.  If the root is null, then the tree is
   -- a simple list not a tree.  Handles null children nodes correctly.
   -- For example, build(a, b, void, c) yields tree (a b c).  build(void,a,b)
   --  yields tree (nil a b).

   make( nodes : $ARR{AST} ) : AST is
      if ( void(nodes) or nodes.size = 0 ) then
	 return void;
      end;

      root : AST := nodes[0];
      tail : AST;

      if ( ~void(root) ) then
	 root.first_child(void); -- don't leave any old pointers set
      end;

      -- link in children;
      ni : AST;
      i : INT;
      loop i := 1.upto!( nodes.size - 1);

	 ni := nodes[i];
	 -- ni := nodes.elt!; -- can't use elt! since it starts from index 0

	 if ( ~void(ni) ) then -- ignore null nodes
	    if ( void(root) ) then
	       -- Set the root and set it up for a flat list
	       tail := ni;
	       root := tail;
	    elsif ( void(tail) ) then
	       root.first_child(ni);
	       tail := root.first_child;
	    else 
	       tail.next_sibling(ni);
	       tail := tail.next_sibling;
	    end;

	    -- Chase tail to last sibling
	    loop while! ( ~void(tail.next_sibling) ); 
	       tail := tail.next_sibling;
	    end;
	 end;
      end;
      return root;
   end;

end;