Subversion Repositories programming

#!/usr/bin/env python

# Copyright: 2006 Ira W. Snyder
# Start Date: 2006-02-01
# License: GNU General Public License v2 (or at your option, any later version)
#

parsing_table = (('', 'BEGIN', 'END', 'IF', 'ELSE', 'WHILE', 'ID', 'READ', 'WRITE', 'NUM', '+', '(', ')', ';', '=', '$'),
                 ('program', 1, '', '', '', '', '', '', '', '', '', '', '', '', '', ''),
                 ('stmtseq', '', '', 2, '', 2, 2, 2, 2, '', '', '', '', '', '', ''),
                 ('stmtseq1', '', 4, '', '', '', '', '', '', '', '', '', '', 3, '', ''),
                 ('stmt', '', '', 5, '', 6, 7, 8, 9, '', '', '', '', '', '', ''),
                 ('exp', '', '', '', '', '', 10, '', '', 10, '', 10, '', '', '', ''),
                 ('exp1', '', 12, '', 12, '', '', '', '', '', 11, '', 12, 12, '', ''),
                 ('term', '', '', '', '', '', 15, '', '', 14, '', 13, '', '', '', ''))

def terminals():
    """Return a list of the terminals in the table"""

    return [n for n in parsing_table[0] if n != '']

def nonterminals():
    """Return a list of non-terminals in the table"""

    return [n[0] for n in parsing_table if n[0] != '']

def LL1_Parsing_Algo ():
    """This implements the table-based LL(1) parsing algorithm from Figure 4.2
    (Page 155) in Compiler Construction Principles and Practices"""

    END_SYMBOL = '$'
    s = Stack()
    s.push(START_SYMBOL)

    #while s.peek() != END_SYMBOL and input.getNextToken() != END_SYMBOL:
    #    pass
    
class InputParser:
    """Implements a simple tokenizer for the TOY language"""

    def __init__(self, inputstr):
        self.__inputstr = inputstr

    def getNextToken(self):
        """Gets the first token off of the front of the input string, but
        DOES NOT remove any input."""
        pass

    def match(self):
        """A match has happened, so remove the front of the input string."""
        pass

class Stack:
    """Implements a simple stack using a list"""

    def __init__(self):
        self.__data = []

    def push(self, val):
        """Push a value onto the top of the stack"""
        self.__data.append(val)

    def pop(self):
        """Pop a value off the top of the stack.
        WARNING: throws IndexError if there is nothing left in the stack"""
        return self.__data.pop()

    def peek(self):
        """Peek at the top of the stack. Basically a pop() without removing the
        object from the top.
        WARNING: will throw an IndexError if there is nothing left in the stack."""

        temp = self.pop()
        self.push(temp)
        return temp

################################################################################
################################################################################
################################################################################
################################################################################
################################################################################

def main():
    """The main function for this program"""

    print terminals()
    print nonterminals()
   
if __name__ == '__main__':
    main()