def if_else(self, if_: Filter[X],
then: Function[X, Y],
else_: Function[X, Y] = identity) -> 'Stream[Y]':
"""
if "if_" returns True then elements are transformed according to "then" otherwise else_
function is used. This method is the special case of "conditional" method.
"else_" has default value "identity" which return element as it is in case "if_" fails;
Example:
Stream(range(10)).condition(lambda x: 3 <= x <= 7, lambda x: 1 , lambda x: 0).collect(ToList())
-> [0, 0, 0, 1, 1, 1, 1, 1, 0, 0]
:param if_:
:param then:
:param else_: by default it returns element as it is.
:return: Stream itself
"""
return self.map(ChainedCondition.if_else(if_, then, else_))
def test_map7(self):
rnd = self.rnd
a, b, size = 1, 100, 50
cc = (ChainedCondition.if_else(lambda x: x < 50, lambda x: x**2,
lambda x: x % 50))
out = Stream(rnd.int_range_supplier(a, b)) \
.limit(size) \
.conditional(cc) \
.reduce(op.mul, 1) \
.get()
rnd.reset()
data = (cc(e) for e in rnd.int_range(a, b, size=size))
out_target = reduce(op.mul, data)
self.assertEqual(out, out_target)