def get_sexpr(self, source=None):
if source:
self.raw_source = source
self.length = len(self.raw_source)
self.index = 0
token = self.get_token()
expr = None
if token == ')':
raise ValueError("Unexpected right paren")
elif token == '(':
expr = []
token = self.get_token()
while token != ')':
if token == '(':
# Start parsing again.
self.prev()
expr.append(self.get_sexpr())
elif token == None:
raise ValueError("Invalid end of expression: ", self.raw_source)
else:
expr.append(token)
token = self.get_token()
return List(expr)
else:
return token
class Symbol(Atom):
def __init__(self, symbol):
super(Symbol, self).__init__(symbol)
def __repr__(self):
return self.data
def __hash__(self):
return hash(self.data)
def eval(self, env, args=None):
return env.get(self.data)
TRUE = Symbol('#t')
FALSE = List()
class String(Atom, Sequence):
def __init__(self, str):
Atom.__init__(self, str)
def __repr__(self):
return repr(self.data)
def eval(self, env, args=None):
return self
def cons(self, e):
if e.__class__ != self.__class__ and e.__class__ != Symbol.__class__:
raise UnimplementedFunctionError('Cannot cons a string and a ',
def cons(self, e):
ret = List(self.data[:]) # bugfix 1234977437
ret.data.insert(0, e)
return ret
def test_falsiness(self):
self.assertEquals(FALSE, List())
def cdr(self):
try:
return List(self.data[1:])
except:
return List([])