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+    May 2018
+Lambda Calculus
+===============
+
+Playing with Type Quantifiers and Haskell's Rank 2 Type Polymorphsim,
+implementing Boolean logic from scratch. We use the conventional 
+definitions for `True` an `False` also known as Church booleans, after Alonzo Church, who 
+intruced them along Lambda Calculus in the 1930s [[1]](#ref).
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ {.haskell .numberLines}
+{-# LANGUAGE Rank2Types #-}
+
+fTrue :: forall a. a->a->a
+fTrue   x y = x
+
+fFalse :: forall a. a->a->a
+fFalse  x y = y
+
+fAnd :: (forall a. a->a->a)->(forall a. a->a->a)->(forall a. a->a->a)
+fAnd p q = p q p
+
+fOr :: (forall a. a->a->a)->(forall a. a->a->a)->(forall a. a->a->a)
+fOr p q = p p q
+
+fNot :: (forall a. a->a->a)->(forall a. a->a->a)
+fNot p = p fFalse fTrue
+
+ifThenElse :: (forall a. a->a->a)->(forall a. a->a->a)
+            ->(forall a. a->a->a)->(forall a. a->a->a)
+ifThenElse p a b = p a b
+
+-- Example --
+
+main = print $ (ifThenElse fFalse fFalse $ fAnd fTrue $ fNot fFalse) "T" "F"
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+## Ref
+
+* [1] <https://en.wikipedia.org/wiki/Lambda_calculus>