Data commit

Task/Cheryls-birthday/Python/cheryls-birthday.py

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+'''Cheryl's Birthday'''
+
+from itertools import groupby
+from re import split
+
+
+# main :: IO ()
+def main():
+    '''Derivation of the date.'''
+
+    month, day = 0, 1
+    print(
+        # (3 :: A "Then I also know")
+        # (A's month contains only one remaining day)
+        uniquePairing(month)(
+            # (2 :: B "I know now")
+            # (B's day is paired with only one remaining month)
+            uniquePairing(day)(
+                # (1 :: A "I know that Bernard does not know")
+                # (A's month is not among those with unique days)
+                monthsWithUniqueDays(False)([
+                    # 0 :: Cheryl's list:
+                    tuple(x.split()) for x in
+                    split(
+                        ', ',
+                        'May 15, May 16, May 19, ' +
+                        'June 17, June 18, ' +
+                        'July 14, July 16, ' +
+                        'Aug 14, Aug 15, Aug 17'
+                    )
+                ])
+            )
+        )
+    )
+
+
+# ------------------- QUERY FUNCTIONS --------------------
+
+# monthsWithUniqueDays :: Bool -> [(Month, Day)] -> [(Month, Day)]
+def monthsWithUniqueDays(blnInclude):
+    '''The subset of months with (or without) unique days.
+    '''
+    def go(xs):
+        month, day = 0, 1
+        months = [fst(x) for x in uniquePairing(day)(xs)]
+        return [
+            md for md in xs
+            if blnInclude or not (md[month] in months)
+        ]
+    return go
+
+
+# uniquePairing :: DatePart -> [(Month, Day)] -> [(Month, Day)]
+def uniquePairing(i):
+    '''Subset of months (or days) with a unique intersection.
+    '''
+    def go(xs):
+        def inner(md):
+            dct = md[i]
+            uniques = [
+                k for k in dct.keys()
+                if 1 == len(dct[k])
+            ]
+            return [tpl for tpl in xs if tpl[i] in uniques]
+        return inner
+    return ap(bindPairs)(go)
+
+
+# bindPairs :: [(Month, Day)] ->
+# ((Dict String [String], Dict String [String])
+# -> [(Month, Day)]) -> [(Month, Day)]
+def bindPairs(xs):
+    '''List monad injection operator for lists
+       of (Month, Day) pairs.
+    '''
+    return lambda f: f(
+        (
+            dictFromPairs(xs),
+            dictFromPairs(
+                [(b, a) for (a, b) in xs]
+            )
+        )
+    )
+
+
+# dictFromPairs :: [(Month, Day)] -> Dict Text [Text]
+def dictFromPairs(xs):
+    '''A dictionary derived from a list of
+       month day pairs.
+    '''
+    return {
+        k: [snd(x) for x in m] for k, m in groupby(
+            sorted(xs, key=fst), key=fst
+        )
+    }
+
+
+# ----------------------- GENERIC ------------------------
+
+# ap :: (a -> b -> c) -> (a -> b) -> a -> c
+def ap(f):
+    '''Applicative instance for functions.
+    '''
+    def go(g):
+        def fxgx(x):
+            return f(x)(
+                g(x)
+            )
+        return fxgx
+    return go
+
+
+# fst :: (a, b) -> a
+def fst(tpl):
+    '''First component of a pair.
+    '''
+    return tpl[0]
+
+
+# snd :: (a, b) -> b
+def snd(tpl):
+    '''Second component of a pair.
+    '''
+    return tpl[1]
+
+
+if __name__ == '__main__':
+    main()