Data commit

Task/Humble-numbers/Python/humble-numbers.py

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+'''Humble numbers'''
+
+from itertools import groupby, islice
+from functools import reduce
+
+
+# humbles :: () -> [Int]
+def humbles():
+    '''A non-finite stream of Humble numbers.
+       OEIS A002473
+    '''
+    hs = set([1])
+    while True:
+        nxt = min(hs)
+        yield nxt
+        hs.remove(nxt)
+        hs.update(nxt * x for x in [2, 3, 5, 7])
+
+
+# TEST ----------------------------------------------------
+# main :: IO ()
+def main():
+    '''First 50, and counts with N digits'''
+
+    print('First 50 Humble numbers:\n')
+    for row in chunksOf(10)(
+            take(50)(humbles())
+    ):
+        print(' '.join(map(
+            lambda x: str(x).rjust(3),
+            row
+        )))
+
+    print('\nCounts of Humble numbers with n digits:\n')
+    for tpl in take(10)(
+            (k, len(list(g))) for k, g in
+            groupby(len(str(x)) for x in humbles())
+    ):
+        print(tpl)
+
+
+# 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
+       divible, the final list will be shorter than n.
+    '''
+    return lambda xs: reduce(
+        lambda a, i: a + [xs[i:n + i]],
+        range(0, len(xs), n), []
+    ) if 0 < n else []
+
+
+# take :: Int -> [a] -> [a]
+# take :: Int -> String -> String
+def take(n):
+    '''The prefix of xs of length n,
+       or xs itself if n > length xs.
+    '''
+    return lambda xs: (
+        list(islice(xs, n))
+    )
+
+
+# MAIN ---
+if __name__ == '__main__':
+    main()