Updates:
Status: WontFix
Comment #4 on issue 4019 by [email protected]: divisors could use a 'pairs'
flag
http://code.google.com/p/sympy/issues/detail?id=4019
def divisor_pairs(n):
"""Return pairs of divisors of n, (a, b), such that a <= b. A
generator of pairs (not necessarily in order) is returned.
Examples
========
>>> from sympy import divisor_pairs
>>> list(divisor_pairs(24))
[(1, 24), (2, 12), (4, 6), (3, 8)]
"""
for d in divisors(n, generator=True):
if d <= n//d:
yield (d, n // d)
But perhaps this is just something that should go in one's personal
library. A one-liner in spirit of yours is
n=120
[(d, n//d) for d in divisors(n, True) if d <= n//d]
[(1, 120), (2, 60), (4, 30), (8, 15), (3, 40), (6, 20), (5, 24), (10, 12)]
I'll close this unless there is a second to add such a function. As a point
of reference, Wolfram has lots of utility functions related to divisors,
like "common divisors of A and B" and "common multiples of A and B".
Perhaps this gets down to questions about what qualifies as being a useful
tool in the CAS environment. Just being able to get the divisors (or lcm or
gcd) is enough to do more complex tasks. But whether the codebase should
have those added or not is the question.
In teaching algebra, it makes sense to look at divisor pairs rather than
just the divisors.
So...if anyone else thinks this should be in SymPy I will submit a patch,
otherwise this is closed.
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