Evaluate binomial coefficients: Difference between revisions

Or, updating for Python 3, and abstracting a little more for legibility and ease of reuse, while currying for ease of mapping and general composition:

<lang python>from functools import reduce

# binomialCoefficient :: Int -> Int -> Int

def binomialCoefficient(n):

return lambda k: product(

enumFromTo(1 + k)(n)

) // factorial(n - k)

# GENERIC -------------------------------------------------

# enumFromTo :: Int -> Int -> [Int]

def enumFromTo(m):

return lambda n: range(m, 1 + n)

# factorial :: Int -> Int

def factorial(x):

return product(enumFromTo(1)(x))

# product :: [Num] -> Num

def product(xs):

return reduce(lambda a, b: a * b, xs, 1)

# TESTS ---------------------------------------------------

print(

binomialCoefficient(5)(3)

)

# k=0 to k=5, where n=5

print(

list(map(

binomialCoefficient(5),

enumFromTo(0)(5)

))

)</lang>

{{Out}}

<pre>10

[1, 5, 10, 10, 5, 1]</pre>