def _preform_comparison(func, *args):
if len(args) == 1:
return Boolean(True)
prev, rest = args[0], args[1:]
for arg in rest:
if not func(prev, arg):
return Boolean(False)
prev = arg
return Boolean(True)
def _eval_and(self, expr, env):
if procedure.no_operands(procedure.operands(expr)):
return Boolean(True)
def inner(expr, env):
if sequence.is_last_expr(expr):
return self._eval(sequence.first_expr(expr), env)
if not self._eval(sequence.first_expr(expr), env):
return Boolean(False)
return inner(sequence.rest_exprs(expr), env)
return inner(sequence.rest_exprs(expr), env)
def _eval_or(self, expr, env):
if procedure.no_operands(procedure.operands(expr)):
return Boolean(False)
def inner(expr, env):
if sequence.is_last_expr(expr):
return self._eval(sequence.first_expr(expr), env)
first_value = self._eval(sequence.first_expr(expr), env)
if first_value:
return first_value
return inner(sequence.rest_exprs(expr), env)
return inner(sequence.rest_exprs(expr), env)
def expand_clauses(clauses):
if clauses is EmptyList:
return Boolean(False)
first = car(clauses)
rest = cdr(clauses)
if is_cond_else_clause(first):
if rest is EmptyList:
return sequence_expr(cond_actions(first))
else:
raise ValueError('ELSE caluse isn\'t last: %s' % clauses)
else:
return make_if(cond_predicate(first),
sequence_expr(cond_actions(first)), expand_clauses(rest))
def _simple_datum(self):
token = self._lookahead_token(0)
if token.type == tokens.NUMBER:
expr = Number(int(token.text))
elif token.type == tokens.BOOLEAN:
expr = Boolean(True if token.text == '#t' else False)
elif token.type == tokens.CHARACTER:
expr = Character(token.text[2:])
elif token.type == tokens.STRING:
expr = String(token.text.strip('"'))
elif token.type == tokens.ID:
expr = Symbol(token.text)
else:
raise ParserException('No viable alternative')
self._match(token.type)
return expr
def inner(expr, env):
if sequence.is_last_expr(expr):
return self._eval(sequence.first_expr(expr), env)
if not self._eval(sequence.first_expr(expr), env):
return Boolean(False)
return inner(sequence.rest_exprs(expr), env)
def builtin_null_p(*args):
return Boolean(args[0] is EmptyList)
def builtin_pair_p(*args):
arg = args[0]
return Boolean(isinstance(arg, Pair))
def builtin_even_p(*args):
return Boolean(args[0].val % 2 == 0)
def builtin_number_p(*args):
return Boolean(isinstance(args[0], Number))
def builtin_zero_p(*args):
return Boolean(args[0] == Number(0))
def builtin_eq_p(*args):
first, second = args
return Boolean(first == second)
def builtin_not(*args):
return Boolean(not bool(args[0]))