/******************************************************************
 This program implements and tests a recursive descent parser for a
   language defined by a grammar given below.  Testing is done by
   constructing a ParseTree and inspecting the result by calling
   the functions "traverse" and "displayYield".
 The ParseTree construtor takes as its argument the name of a text file.
   It attempts to parse the text as a program in the language generated
   by the grammar. If the parse is successful, a representation of a
   parse tree is returned.  Otherwise an error message is printed, and
   a dummy tree is returned.
 The function "traverse" simply prints the tree if there is one (i.e.,
   if its input is not a dummy).  Otherwise it prints an error message.
 The function "displayYield" returns a list of the tokens in the leaves
   of a parse tree (from left to right).  This should be the list of
   tokens in the string that was parsed.
 The "main" function simply tests the functions by calling it with
   a number of different text files.  Each file is expected to be in
   the current directory.
******************************************************************/


// The grammar for the language is given below.  Here nonterminals are
//   capitalized.  The grammar has been expanded so that in each rule,
//   only tokens appear on the RHS of the arrow.
// The start symbol is "Conditional".

// Conditional -> ShortIf RestIf
// ShortIf -> if Test then Block
// RestIf -> else Block endif
// RestIf -> endif
// Test -> < Var Op Var>
// Var -> x
// Var -> y
// Var -> z
// Op -> =
// Op -> /=
// Block -> begin RestBlock
// RestBlock -> end
// RestBlock -> Statement Statements
// Statements -> end
// Statements -> Statement Statements
// Statement -> Var := Var




////////////////////////////////// The "main" function ////////////////////////////////////////////////////

class A4
{

  public static void main(String args[])             {
  ParseTree t;
    t=new ParseTree("data1.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data2.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data3.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data4.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data5.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data6.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data7.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data8.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data9.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data10.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data11.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data12.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data13.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data14.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data15.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data16.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();
    t=new ParseTree("data17.txt");
    t.traverse();
    System.out.println();
    t.displayYield();
    System.out.println();                             }
}