Munchausen numbers: Difference between revisions

Or, defining an '''isMunchausen''' predicate in terms of a fold, (and reaching for a specialised '''digitToInt''', which turns out to be a little faster than applying the more general built-in '''int()''')

<lang python>from functools import (reduce)

# isMuchausen :: Int -> Bool

def isMunchausen(n):

return n == foldl(

lambda n: lambda c: (lambda v=digitToInt(c): n + v**v)()

)(0)(str(n))

# main :: IO ()

def main():

print (

filter(isMunchausen, xrange(5000))

)

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

# digitToInt :: Char -> Int

def digitToInt(c):

oc = ord(c)

if 48 > oc or 102 < oc:

return None

else:

dec = oc - ord('0')

hexu = oc - ord('A')

hexl = oc - ord('a')

return dec if 9 >= dec else (

10 + hexu if 0 <= hexu and 5 >= hexu else (

10 + hexl if 0 <= hexl and 5 >= hexl else None

)

)

# foldl :: (a -> b -> a) -> a -> [b] -> a

def foldl(f):

return lambda a: lambda xs: (

reduce(lambda x, y: f(x)(y), xs, a)

)

main()

</lang>

<pre>[1, 3435]</pre>