Talk:Weird numbers: Difference between revisions

: PS I think we may be able to see and test the operation of '''hasSum''' more clearly if we enrich its type from Bool to [Int] (with a return the empty list for '''False''', and the integers of the first sum found for '''True'''. Let's call this richer-typed variant '''anySum''', and sketch it in Python 3.

::<lang python># anySum :: Int -> [Int] -> [Int]

def anySum(n, xs):

'''First subset of xs found to sum to n.

(Probably more efficient where the xs are sorted in descending

order of magnitude)'''

def go(n, xs):

if xs:

# Assumes Python 3 for list deconstruction

# Otherwise: h, t = xs[0], xs[1:]

h, *t = xs

if n < h:

return go(n, t)

else:

if n == h:

return [h]

else:

ys = go(n - h, t)

return [h] + ys if ys else go(n, t)

else:

return []

return go(n, xs)

print(anySum(7, [1,1,1,1,1,6]))

# -> [1, 6]</lang>