# How to represent the infinite ?

Thu Jun 20 14:23:28 EDT 2002

```On Thu, 20 Jun 2002 17:02:33 +0200
erreur wrote:

> Will somebody have an idea, to represent the infinite one?
>
> I have variables to initialize with is +inf (or - inf).  To be sure that
> later, all will be smaller (or larger) than my variables.
> I tried to redefine the operators on an object.  It goes for Inf>10 but I do
> not arrive for 10>Inf (because that takes > of Int).
>
> --------------------
>
> def __gt__(self, val):
>
>     return 1
>
> --------------------

Here's a more complete infinite value (not that you'd need it, judging from

class inf(int):
def __init__(self):
int.__init__(self)
self.sign = 1

def __str__(self):
return "<%sinfinity>" % {-1: "-", 1: ""}[self.sign]

def __repr__(self):
return str(self)

def __cmp__(self, n):
if isinstance(n, inf):
return cmp(self.sign, n.sign)
return self.sign

def __neg__(self):
retval = inf()
retval.sign = self.sign * -1
return retval

def __mul__(self, n):
retval = inf()
retval.sign = self.sign * cmp(n, 0)
return retval

def __div__(self, n):
return self * n

if isinstance(n, inf):
if n.sign != self.sign:
return 0
return self

def __sub__(self, n):
return self + -n

if __name__ == '__main__':
import sys

m = -inf()
n = inf()

print m
print n
print m * n
print n * n
print m * m

assert(m < n)
assert(n > m)
assert(m == m)
assert(n == n)
assert(m != n)
assert(m < 0)
assert(n > 0)
assert(m != 0)
assert(n
assert(m < -sys.maxint)
assert(n > sys.maxint)
assert(m < -m)
assert(n == -m)

assert(n * 1 == n)
assert(n * 1000 == n)
assert(n * -1 == m)
assert(n * -1000 == m)
assert(n * 0 == 0)
assert(m * 0 == 0)

assert(n / 1 == n)
assert(n / -1 == m)
assert(n / -1000 == m)
assert(m / 1 == m)
assert(m / 1000 == m)
assert(m / -1 == n)
assert(m / -1000 == n)

assert(m + 1 == m)
assert(m - 1 == m)
assert(n + 1 == n)
assert(n - 1 == n)

assert(n + m == 0)
assert(n - m == n)
assert(n - n == 0)
assert(m + m == m)
assert(m - m == 0)
assert(m - n == m)

# print 1 / m # exception: division by zero
# print 1 / n # exception: division by zero

--
Cliff Wells, Software Engineer
Logiplex Corporation (www.logiplex.net)
(503) 978-6726 x308  (800) 735-0555 x308

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