MAB 225 - Computação II - Fabio Mascarenhas

Identidade de Objetos / Iteradores Map, Filtro e Zip (10/05/2011)

IDLE 2.6.2      
>>> class Contador:
    def __init__(self, i=1):
        self.i = i
    def inc(self):
        self.i = self.i + 1
        return self.i
    def dec(self):
        self.i = self.i - 1
        return self.i
    def __add__(self, x):
        return Contador(self.i + x)
    def __sub__(self, x):
        return Contador(self.i - x)
    def __repr__(self):
        return "Valor do contador: %i" % self.i
    def __str__(self):
        return str(self.i)

>>> c1 = Contador()
>>> c2 = Contador()
>>> c3 = c2
>>> c1
Valor do contador: 1
>>> c2
Valor do contador: 1
>>> c3
Valor do contador: 1
>>> c1.inc()
2
>>> c1.inc()
3
>>> c1
Valor do contador: 3
>>> c2.inc()
2
>>> c2
Valor do contador: 2
>>> c1
Valor do contador: 3
>>> c3
Valor do contador: 2
>>> c3.inc()
3
>>> c3
Valor do contador: 3
>>> c2
Valor do contador: 3
>>> c4 = c1 + 1
>>> c4
Valor do contador: 4
>>> c1
Valor do contador: 3
>>> c4.inc()
5
>>> c1.inc()
4
>>> c1
Valor do contador: 4
>>> c4
Valor do contador: 5
>>> ================================ RESTART ================================
>>> def quadrado(x):
	return x * x

>>> map(quadrado, [1,2,3])
[1, 4, 9]
>>> class IterMap2:
	def __init__(self, seq, f):
		self.seq = seq
		self.f = f
		self.iter = seq.__iter__()
	def __iter__(self):
		return IterMap2(self.seq, self.f)
	def next(self):
		elem = self.iter.next()
		val = (self.f)(elem)
		return val

>>> for i in IterMap2([1,2,3], quadrado):
	print i

1
4
9
>>> def impar(x):
	return x % 2 != 0

>>> filter(impar, [1,2,3,4,5,6])
[1, 3, 5]
>>> def filtro(f, seq):
	res = []
	pos = 0
	while pos < len(seq):
		if f(seq[pos]):
			res.append(seq[pos])
		pos = pos + 1
	return res

>>> filtro(impar, [1,2,3,4,5,6])
[1, 3, 5]
>>> class IterFiltro:
	def __init__(self, f, seq):
		self.f = f
		self.seq = seq
		self.pos = 0
	def __iter__(self):
		return IterFiltro(self.f, self.seq)
	def next(self):
		while True:
		    if self.pos >= len(self.seq):
			raise StopIteration
		    if (self.f)(self.seq[self.pos]):
			val = self.seq[self.pos]
			self.pos = self.pos + 1
			return val
	            self.pos = self.pos + 1

>>> for i in IterFiltro(impar, [1,2,3,4,5,6]):
	print i

1
3
5
>>> zip([1,2,3],[4,5,6])
[(1, 4), (2, 5), (3, 6)]
>>> class IterZip:
	def __init__(self, seq1, seq2):
		if len(seq1) != len(seq2):
			raise RangeError
		self.seq1 = seq1
		self.seq2 = seq2
		self.pos = 0
	def __iter__(self):
		return IterZip(self.seq1, self.seq2)
	def next(self):
		if self.pos >= len(self.seq2):
			raise StopIteration
		val = (self.seq1[self.pos], self.seq2[self.pos])
		self.pos = self.pos + 1
		return val

>>> for i in IterZip([1,2,3],[4,5,6]):
	print i
	
(1, 4)
(2, 5)
(3, 6)
>>> def zip(seq1, seq2):
	if len(seq1) != len(seq2):
		raise RangeError
	res = []
	pos = 0
	while pos < len(seq2):
		res.append( (seq1[pos], seq2[pos]) )
		pos = pos + 1
	return res

>>> zip([1,2,3],[4,5,6])
[(1, 4), (2, 5), (3, 6)]
>>>