September Morn Update

Task/Amb/Python/amb-2.py

@@ -0,0 +1,15 @@
+# joins :: String -> String -> Bool
+def joins(a, b):
+    return a[-1] == b[0]
+
+
+print (
+    [
+        ' '.join([w1, w2, w3, w4])
+        for w1 in ['the', 'that', 'a']
+        for w2 in ['frog', 'elephant', 'thing']
+        for w3 in ['walked', 'treaded', 'grows']
+        for w4 in ['slowly', 'quickly']
+        if joins(w1, w2) and joins(w2, w3) and joins(w3, w4)
+    ]
+)

Task/Amb/Python/amb-3.py

@@ -0,0 +1,37 @@
+def main():
+    print (
+        unlines([
+            unwords([w1, w2, w3, w4])
+
+            for w1 in ['the', 'that', 'a']
+            if True
+
+            for w2 in ['frog', 'elephant', 'thing']
+            if joins(w1, w2)
+
+            for w3 in ['walked', 'treaded', 'grows']
+            if joins(w2, w3)
+
+            for w4 in ['slowly', 'quickly']
+            if joins(w3, w4)
+        ])
+    )
+
+
+# joins :: String -> String -> Bool
+def joins(a, b):
+    return a[-1] == b[0]
+
+
+# unlines :: [String] -> String
+def unlines(xs):
+    return '\n'.join(xs)
+
+
+# unwords :: [String] -> String
+def unwords(xs):
+    return ' '.join(xs)
+
+
+if __name__ == '__main__':
+    main()

Task/Amb/Python/amb-4.py

@@ -0,0 +1,79 @@
+from itertools import chain
+
+
+# amb :: [a] -> (a -> [b]) -> [b]
+def amb(xs):
+    return lambda f: list(
+        chain.from_iterable(
+            map(f, xs)
+        )
+    )
+
+
+# main :: IO ()
+def main():
+
+    xs = enumFromTo(1)(10)
+    print ('Pythagorean triples from integers 1-10:')
+    print (
+        amb(xs)(
+            lambda x: amb(xs)
+            (lambda y: amb(xs)
+                (lambda z: when(
+                    x * x + y * y == z * z
+                )(
+                    (x, y, z)
+                )
+            ))
+        )
+    )
+
+    # joins :: String -> String -> Bool
+    def joins(a, b):
+        return a[-1] == b[0]
+
+    print ('\nRC problem given above:')
+    print (
+        amb(['the', 'that', 'a'])(
+            lambda w1: amb(
+                ['frog', 'elephant', 'thing']
+            )(lambda w2: amb(
+                ['walked', 'treaded', 'grows']
+            )(lambda w3: amb(
+                ['slowly', 'quickly']
+            )(lambda w4: when(
+                joins(w1, w2) and joins(w2, w3) and joins(w3, w4)
+            )(
+                (w1, w2, w3, w4)
+            ))))
+        )
+    )
+    print('\nAdditional problem reference in procedural version above:')
+    print(
+        amb([1, 2, 3])
+        (
+            lambda x: amb([4, 5, 6])
+            (
+                lambda y: when(x * y != 8)
+                (
+                    (x, y)
+                )
+            )
+        )
+    )
+
+# GENERIC -------------------------------------------------
+
+
+# enumFromTo :: (Int, Int) -> [Int]
+def enumFromTo(m):
+    return lambda n: list(range(m, 1 + n))
+
+
+# when :: Bool -> [a] -> [a]
+def when(p):
+    return lambda x: [x] if p else []
+
+# MAIN ---
+if __name__ == '__main__':
+    main()

Task/Amb/Python/amb-5.py

@@ -0,0 +1,42 @@
+from itertools import chain
+
+
+# amb :: [a] -> (a -> [b]) -> [b]
+def amb(xs):
+    return lambda f: list(
+        chain.from_iterable(
+            map(f, xs)
+        )
+    )
+
+
+# when :: Bool -> [a] -> [a]
+def when(p):
+    return lambda xs: xs if p else []
+
+
+# TEST ----------------------------------------------------
+
+# joins :: String -> String -> Bool
+def joins(a, b):
+    return a[-1] == b[0]
+
+
+print (
+    amb(['the', 'that', 'a'])(
+        lambda w1: when(True)
+
+        (amb(['frog', 'elephant', 'thing'])
+         (lambda w2: when(joins(w1, w2))
+
+          (amb(['walked', 'treaded', 'grows'])
+           (lambda w3: when(joins(w2, w3))
+
+            (amb(['slowly', 'quickly'])
+             (lambda w4: when(joins(w3, w4))(
+
+                 [w1, w2, w3, w4]
+             ))))))
+         )
+    )
+)