Initial data commit

Task/Rep-string/Python/rep-string-3.py

@@ -0,0 +1,97 @@
+'''Rep-strings'''
+
+from itertools import (accumulate, chain, cycle, islice)
+
+
+# repCycles :: String -> [String]
+def repCycles(s):
+    '''Repeated sequences of characters in s.'''
+    n = len(s)
+    cs = list(s)
+
+    return [
+        x for x in
+        tail(inits(take(n // 2)(s)))
+        if cs == take(n)(cycle(x))
+    ]
+
+
+# TEST ----------------------------------------------------
+# main :: IO ()
+def main():
+    '''Tests - longest cycle (if any) in each string.'''
+    print(
+        fTable('Longest cycles:\n')(repr)(
+            lambda xs: ''.join(xs[-1]) if xs else '(none)'
+        )(repCycles)([
+            '1001110011',
+            '1110111011',
+            '0010010010',
+            '1010101010',
+            '1111111111',
+            '0100101101',
+            '0100100',
+            '101',
+            '11',
+            '00',
+            '1',
+        ])
+    )
+
+
+# GENERIC -------------------------------------------------
+
+# inits :: [a] -> [[a]]
+def inits(xs):
+    '''all initial segments of xs, shortest first.'''
+    return accumulate(chain([[]], xs), lambda a, x: a + [x])
+
+
+# tail :: [a] -> [a]
+# tail :: Gen [a] -> [a]
+def tail(xs):
+    '''The elements following the head of a
+       (non-empty) list or generator stream.'''
+    if isinstance(xs, list):
+        return xs[1:]
+    else:
+        list(islice(xs, 1))  # First item dropped.
+        return xs
+
+
+# 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: (
+        xs[0:n]
+        if isinstance(xs, (list, tuple))
+        else list(islice(xs, n))
+    )
+
+
+# OUTPUT FORMATTING ---------------------------------------
+
+# fTable :: String -> (a -> String) ->
+#                     (b -> String) -> (a -> b) -> [a] -> String
+def fTable(s):
+    '''Heading -> x display function ->
+                 fx display function ->
+          f -> value list -> tabular string.
+    '''
+    def go(xShow, fxShow, f, xs):
+        ys = [xShow(x) for x in xs]
+        w = max(map(len, ys))
+        return s + '\n' + '\n'.join(map(
+            lambda x, y: y.rjust(w, ' ') + ' -> ' + fxShow(f(x)),
+            xs, ys
+        ))
+    return lambda xShow: lambda fxShow: lambda f: lambda xs: go(
+        xShow, fxShow, f, xs
+    )
+
+
+# MAIN ---
+if __name__ == '__main__':
+    main()