Write You a Haskell Stephen Diehl

For instance the following toplevel pattern for the xor function is transformed into the following nested
set of case statements:
-- Frontend
xor False False = False;
xor False True = True;
xor True False = True;
xor True True = False;
-- Desugared
xor :: Bool -> Bool -> Bool
xor = \_a _b -> case _a of {
False -> case _b of {
False -> False;
True -> True
};
True -> case _b of {
False -> True;
True -> False
}
}
Constructor Patterns
Toplevel declarations in the frontend language can consist of patterns for on the right-hand-side of the
declaration, while in the Core language these are transformed into case statements in the body of the
function.
-- Frontend
f (Left l) = a
f (Right r) = b
-- Desugared
f x = case x of
Left l -> a
Right r -> b
Nested Patterns
e frontend language also allows nested constructors in a single pattern, while in the Core language
these are expanded out into two case statements which scrutinize only one level of pattern.
-- Frontend
f x = case x of
Just (Just y) -> y
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