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Description | ||||||||

By importing this module, the user is able to use all the rewriting
machinery. The user is only required to provide an instance of
Consider a datatype representing logical propositions: data Expr = Const Int | Expr :++: Expr | Expr :**: Expr deriving Show An instance of instance Regular Expr where type PF Expr = K Int :+: Id :*: Id :+: Id :*: Id from (Const n) = L (K n) from (e1 :++: e2) = R (L $ (Id e1) :*: (Id e2)) from (e1 :**: e2) = R (R $ (Id e1) :*: (Id e2)) to (L (K n)) = Const n to (R (L ((Id r1) :*: (Id r2)))) = r1 :++: r2 to (R (R ((Id r1) :*: (Id r2)))) = r1 :**: r2 Additionally, the instance instance Rewrite Expr Build rules like this: rule1 :: Rule Expr rule1 = rule $ x -> x :++: Const 0 :~> x rule5 :: Rule Expr rule5 = rule $ x y z -> x :**: (y :++: z) :~> (x :**: y) :++: (x :**: z) And apply them as follows: test1 :: Maybe Expr test1 = rewriteM rule1 (Const 2 :++: Const 0) test10 :: Maybe Expr test10 = rewriteM rule5 ((Const 1) :**: ((Const 2) :++: (Const 3))) You may also wish to add constructor names in the representation to use generic show. However, constructor names are not yet a stable feature and will probably change in future versions of this library. instance Regular Expr where type PF Expr = Con (K Int) :+: Con (Id :*: Id) :+: Con (Id :*: Id) from (Const n) = L (Con "Const" (K n)) from (e1 :++: e2) = R (L (Con "(:++:)" $ (Id e1) :*: (Id e2))) from (e1 :**: e2) = R (R (Con "(:**:)" $ (Id e1) :*: (Id e2))) to (L (Con _ (K n))) = Const n to (R (L (Con _ ((Id r1) :*: (Id r2))))) = r1 :++: r2 to (R (R (Con _ ((Id r1) :*: (Id r2))))) = r1 :**: r2 | ||||||||

Documentation | ||||||||

module Generics.Regular.Rewriting.Base | ||||||||

module Generics.Regular.Rewriting.Machinery | ||||||||

module Generics.Regular.Rewriting.Representations | ||||||||

module Generics.Regular.Rewriting.Rules | ||||||||

module Generics.Regular.Rewriting.Strategies | ||||||||

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