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

class ANTLR_UTIL is
   
   strip_front_back( src, head, tail : STR ) : STR is

      h : INT := src.search( head );
      t : INT := search_backwards( src, tail );
      
      if ( h = -1 or t = -1 ) then 
	 return src;
      end;
      
      beg : INT := h + head.size;
      num : INT := t - beg;
      return src.substring( beg , num );
	 
   end;
   
   -- search backwards by finding the repeatedly searching forwards.
   -- OK, so it isn't the most efficient algorithm, but we'll live with it
   -- for now.
   search_backwards( src, s : STR ) : INT is 

      if ( s.size = 0 ) then
	 return src.size;
      end;
	       
      from  : INT := 0;
      i     : INT := -1;
      index : INT := -1;

      loop
	 i := src.search( s , from );
	 if ( i = -1 ) then
	    break!;
	 end;
	 index := i;
	 from := index + s.size;
      end;
      return index;
   end;
         
end;