def __init__(self, first, last=None, step=None):
AllExpression.__init__(self, step)
first = asint(first)
last = asint(last)
if last is None and step is None:
last = first
if last is not None and first > last:
raise ValueError('The minimum value in a range must not be '
'higher than the maximum')
self.first = first
self.last = last
def __init__(self, step=None):
self.step = asint(step)
if self.step == 0:
raise ValueError('Increment must be higher than 0')