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diff --git a/Haskell-book/24/language-dot/src/Language/Dot/Syntax.hs b/Haskell-book/24/language-dot/src/Language/Dot/Syntax.hs
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+-- | DOT AST. See <http://www.graphviz.org/doc/info/lang.html>.
+
+module Language.Dot.Syntax where
+
+data Graph
+  = Graph GraphStrictness GraphDirectedness (Maybe Id) [Statement]
+  deriving (Eq, Show)
+
+data GraphStrictness
+  = StrictGraph
+  | UnstrictGraph
+  deriving (Eq, Show)
+
+data GraphDirectedness
+  = DirectedGraph
+  | UndirectedGraph
+  deriving (Eq, Show)
+
+data Id
+  = NameId    String
+  | StringId  String
+  | IntegerId Integer
+  | FloatId   Float
+  | XmlId     Xml
+  deriving (Eq, Show)
+
+data Statement
+  = NodeStatement       NodeId [Attribute]
+  | EdgeStatement       [Entity] [Attribute]
+  | AttributeStatement  AttributeStatementType [Attribute]
+  | AssignmentStatement Id Id
+  | SubgraphStatement   Subgraph
+  deriving (Eq, Show)
+
+data AttributeStatementType
+  = GraphAttributeStatement
+  | NodeAttributeStatement
+  | EdgeAttributeStatement
+  deriving (Eq, Show)
+
+data Attribute
+  = AttributeSetTrue  Id
+  | AttributeSetValue Id Id
+  deriving (Eq, Show)
+
+data NodeId
+  = NodeId Id (Maybe Port)
+  deriving (Eq, Show)
+
+data Port
+  = PortI Id (Maybe Compass)
+  | PortC Compass
+  deriving (Eq, Show)
+
+data Compass
+  = CompassN  | CompassE  | CompassS  | CompassW
+  | CompassNE | CompassNW | CompassSE | CompassSW
+  deriving (Eq, Show)
+
+data Subgraph
+  = NewSubgraph (Maybe Id) [Statement]
+  | SubgraphRef Id
+  deriving (Eq, Show)
+
+data Entity
+  = ENodeId   EdgeType NodeId
+  | ESubgraph EdgeType Subgraph
+  deriving (Eq, Show)
+
+data EdgeType
+  = NoEdge
+  | DirectedEdge
+  | UndirectedEdge
+  deriving (Eq, Show)
+
+data Xml
+  = XmlEmptyTag XmlName [XmlAttribute]
+  | XmlTag      XmlName [XmlAttribute] [Xml]
+  | XmlText     String
+  deriving (Eq, Show)
+
+data XmlName
+  = XmlName String
+  deriving (Eq, Show)
+
+data XmlAttribute
+  = XmlAttribute XmlName XmlAttributeValue
+  deriving (Eq, Show)
+
+data XmlAttributeValue
+  = XmlAttributeValue String
+  deriving (Eq, Show)