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|
{-|
Derives an instance of @Monoid@. It uses the product
construction of monoids. @mappend@ on two different constructors
is undefined.
-}
module Data.Derive.Monoid(makeMonoid) where
{-
import Data.Monoid hiding (First)
example :: Sample
instance Monoid a => Monoid (Sample a) where
mempty = head [First, Second (const mempty 1) (const mempty 2), Third (const mempty 1)]
mappend (First) (First) = First
mappend (Second x1 x2) (Second y1 y2) = Second (mappend x1 y1) (mappend x2 y2)
mappend (Third x1) (Third y1) = Third (mappend x1 y1)
mappend _ _ | length [First{},Second{},Third{}] > 1 = error "Monoid.mappend: Different constructors for Sample"
-}
-- GENERATED START
import Data.Derive.DSL.DSL
import Data.Derive.Internal.Derivation
makeMonoid :: Derivation
makeMonoid = derivationDSL "Monoid" dslMonoid
dslMonoid =
List [Instance ["Monoid"] "Monoid" (List [App "InsDecl" (List [App
"PatBind" (List [App "PVar" (List [App "Ident" (List [String
"mempty"])]),App "Nothing" (List []),App "UnGuardedRhs" (List [App
"App" (List [App "Var" (List [App "UnQual" (List [App "Ident" (
List [String "head"])])]),App "List" (List [MapCtor (Application (
Concat (List [List [App "Con" (List [App "UnQual" (List [App
"Ident" (List [CtorName])])])],MapField (App "Paren" (List [
Application (List [App "Var" (List [App "UnQual" (List [App
"Ident" (List [String "const"])])]),App "Var" (List [App "UnQual"
(List [App "Ident" (List [String "mempty"])])]),App "Lit" (List [
App "Int" (List [FieldIndex])])])]))])))])])]),App "BDecls" (List
[List []])])]),App "InsDecl" (List [App "FunBind" (List [Concat (
List [MapCtor (App "Match" (List [App "Ident" (List [String
"mappend"]),List [App "PParen" (List [App "PApp" (List [App
"UnQual" (List [App "Ident" (List [CtorName])]),MapField (App
"PVar" (List [App "Ident" (List [Concat (List [String "x",ShowInt
FieldIndex])])]))])]),App "PParen" (List [App "PApp" (List [App
"UnQual" (List [App "Ident" (List [CtorName])]),MapField (App
"PVar" (List [App "Ident" (List [Concat (List [String "y",ShowInt
FieldIndex])])]))])])],App "Nothing" (List []),App "UnGuardedRhs"
(List [Application (Concat (List [List [App "Con" (List [App
"UnQual" (List [App "Ident" (List [CtorName])])])],MapField (App
"Paren" (List [Application (List [App "Var" (List [App "UnQual" (
List [App "Ident" (List [String "mappend"])])]),App "Var" (List [
App "UnQual" (List [App "Ident" (List [Concat (List [String "x",
ShowInt FieldIndex])])])]),App "Var" (List [App "UnQual" (List [
App "Ident" (List [Concat (List [String "y",ShowInt FieldIndex])])
])])])]))]))]),App "BDecls" (List [List []])])),List [App "Match"
(List [App "Ident" (List [String "mappend"]),List [App "PWildCard"
(List []),App "PWildCard" (List [])],App "Nothing" (List []),App
"GuardedRhss" (List [List [App "GuardedRhs" (List [List [App
"Qualifier" (List [App "InfixApp" (List [App "App" (List [App
"Var" (List [App "UnQual" (List [App "Ident" (List [String
"length"])])]),App "List" (List [MapCtor (App "RecConstr" (List [
App "UnQual" (List [App "Ident" (List [CtorName])]),List []]))])])
,App "QVarOp" (List [App "UnQual" (List [App "Symbol" (List [
String ">"])])]),App "Lit" (List [App "Int" (List [Int 1])])])])],
App "App" (List [App "Var" (List [App "UnQual" (List [App "Ident"
(List [String "error"])])]),App "Lit" (List [App "String" (List [
Concat (List [String "Monoid.mappend: Different constructors for "
,DataName])])])])])]]),App "BDecls" (List [List []])])]])])])])]
-- GENERATED STOP
|
