Driving the LogPy logic package using a simple Omega parser. I'm probably being silly and naive, but it's fun. https://github.com/logpy/logpy https://gitorious.org/python-omega/

om.py

#!/usr/bin/env python
from omega import BaseParser
from logpy import run, eq, membero, var, conde
# Still TODO: membero and conde


#: Namespace for storing logic variable as they are defined.
variables = {}


def define(name, namespace=variables):
  '''
  Return a named logic variable in the namespace.
  '''
  return namespace.setdefault(name, var(name))


def _run(n, t, *eqs):
  '''Occasionally it's nice to look at the eqs.'''
  print eqs
  return run(n, t, *eqs)


class LogicParser(BaseParser):
  __grammar = '''

    # Cribbed "spaces" rule from omega.bootstrap.OmegaParser
    spaces = (' ' | '\r' | '\n' | '\t')* -> ' ' ;


    digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' ; 

    digits          = digit+:ds -> ("".join(ds));  
    optional_digits = digit*:ds -> ("".join(ds));  

    number = digits:i '.' optional_digits:f -> (float(i + '.' + f)) |
                               '.' digits:f -> (float('.' + f)) |
                                   digits:i -> (int(i)) ;  


    char = anything:ch ?('a' <= ch <= 'z') -> (ch) ;

    variable = char+:chs -> (define(''.join(chs))) ;

    group = '(' termite+:T ')' -> (tuple(T)) ;

    termite = ' '* (group | variable | number) ;


    EQ = spaces termite:a ' '* "=" termite:b -> ((eq, a, b)) ;

    query =  spaces variable:x ' '* "?" -> (x) ;

    logic = EQ*:eqs query:x spaces -> (run(0, x, *eqs)) ;

    '''

if __name__ == '__main__':
  print (23.2,) == LogicParser.match('''

    a = b
    a = 23.2
    b?

  ''')

  print (2.0,) == LogicParser.match('''

    a = b
    2. = a
    b?

  ''')

  print (0.23,) == LogicParser.match('''

    b = a
    a = .23
    b?

  ''')

  print (1,) == LogicParser.match('''

    (b 2) = (1 2)
    b?

  ''')

  print (2,) == LogicParser.match('''

    (1 b 3) = (1 2 3)
    b?

  ''')

  print (2,) == LogicParser.match('''

    (1 (a 3)) = (1 (2 3))
    a ?

  ''')

  print ((1, 3),) == LogicParser.match('''

    b = (1 3)
    (1 (a 3)) = (1 (b 3))
    a?

  ''')

  print (2,) == LogicParser.match('''

    b = (2 3)
    (1 (a 3)) = (1 b)
    a?

  ''')