Product of min and max prime factors: Difference between revisions
Product of min and max prime factors (view source)
Revision as of 22:15, 5 November 2022
, 1 year ago→{{header|Python}}: Added a functionally composed variant.
(multiplicative identity - compare math.prod([]) in Python) |
(→{{header|Python}}: Added a functionally composed variant.) |
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Line 1,479:
=={{header|Python}}==
===Procedural===
<syntaxhighlight lang="python">''' Rosetta code rosettacode.org/wiki/Product_of_min_and_max_prime_factors '''
Line 1,503 ⟶ 1,504:
91 46 93 94 95 6 9409 14 33 10
</pre>
===Functional===
Defining an infinite series, tabulating with flexible column widths for larger samples,
and writing (rather than importing) a primeFactors function:
<syntaxhighlight lang="python">'''Produce of min and max prime factors'''
from itertools import chain, count, islice
from math import floor, sqrt
# oeisA066048 :: [Int]
def oeisA066048():
'''Infinite series of terms in OEIS A066048.
'''
def f(x):
ns = primeFactors(x)
return ns[0] * ns[-1]
return chain([1], map(f, count(2)))
# ------------------------- TEST -------------------------
# main :: IO ()
def main():
'''First 100 terms in OEIS A066048.
'''
print(table(10)(
list(map(
str, islice(
oeisA066048(),
100
)
))
))
# ----------------------- GENERIC ------------------------
# chunksOf :: Int -> [a] -> [[a]]
def chunksOf(n):
'''A series of lists of length n, subdividing the
contents of xs. Where the length of xs is not evenly
divisible, the final list will be shorter than n.
'''
def go(xs):
return (
xs[i:n + i] for i in range(0, len(xs), n)
) if 0 < n else None
return go
# primeFactors :: Int -> [Int]
def primeFactors(n):
'''A list of the prime factors of n.
'''
def f(qr):
r = qr[1]
return step(r), 1 + r
def step(x):
return 1 + (x << 2) - ((x >> 1) << 1)
def go(x):
root = floor(sqrt(x))
def p(qr):
q = qr[0]
return root < q or 0 == (x % q)
q = until(p)(f)(
(2 if 0 == x % 2 else 3, 1)
)[0]
return [x] if q > root else [q] + go(x // q)
return go(n)
# table :: Int -> [String] -> String
def table(n):
'''A list of strings formatted as
right-justified rows of n columns.
'''
def go(xs):
w = len(max(xs, key=len))
return '\n'.join(
' '.join(row) for row in chunksOf(n)([
s.rjust(w, ' ') for s in xs
])
)
return go
# until :: (a -> Bool) -> (a -> a) -> a -> a
def until(p):
'''The result of repeatedly applying f until p holds.
The initial seed value is x.
'''
def go(f):
def g(x):
v = x
while not p(v):
v = f(v)
return v
return g
return go
# MAIN ---
if __name__ == '__main__':
main()</syntaxhighlight>
{{Out}}
<pre> 1 4 9 4 25 6 49 4 9 10
121 6 169 14 15 4 289 6 361 10
21 22 529 6 25 26 9 14 841 10
961 4 33 34 35 6 1369 38 39 10
1681 14 1849 22 15 46 2209 6 49 10
51 26 2809 6 55 14 57 58 3481 10
3721 62 21 4 65 22 4489 34 69 14
5041 6 5329 74 15 38 77 26 6241 10
9 82 6889 14 85 86 87 22 7921 10
91 46 93 94 95 6 9409 14 33 10</pre>
=={{header|Quackery}}==
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