{-# LANGUAGE UnicodeSyntax, FlexibleContexts, FlexibleInstances, TypeSynonymInstances, MultiParamTypeClasses #-} -- | Enquiry of the graph structure. Note: In this module the term "node" is often used synonymously to "node reference" and "node value". The two can easily distinguished by their type: the former has type 'Node' the latter usually 'n'. module GraphRewriting.Graph.Read (module GraphRewriting.Graph.Read, module GraphRewriting.Graph.Types, module Data.View) where import Prelude.Unicode import GraphRewriting.Graph.Types import GraphRewriting.Graph.Internal import Control.Monad.Reader import qualified Data.IntMap as Map import qualified Data.IntSet as Set import Data.View import Data.List (nub) type WithGraph n = Reader (Graph n) -- | This forces the use of the 'Reader' monad. Wrapping a sequence of monadic read-only operations (such as those defined below) into a read-only block can save much overhead e.g. in the state monad. readOnly ∷ WithGraph n a → Rewrite n a readOnly r = liftM (runReader r) ask readNode ∷ MonadReader (Graph n) m ⇒ Node → m n readNode (Node n) = readRef n =<< asks nodeMap -- | a wrapper to 'inspect' the given node inspectNode ∷ (View v n, MonadReader (Graph n) m) ⇒ Node → m v inspectNode = liftM inspect . readNode -- | a wrapper to 'examine' the given node examineNode ∷ (View v n, MonadReader (Graph n) m) ⇒ (v → a) → Node → m a examineNode f = liftM (examine f) . readNode -- | all of the graph's nodes readNodeList ∷ MonadReader (Graph n) m ⇒ m [Node] readNodeList = liftM (map Node . Map.keys) (asks nodeMap) -- | all of the graph's edges readEdgeList ∷ MonadReader (Graph n) m ⇒ m [Edge] readEdgeList = liftM (map Edge . Map.keys) (asks edgeMap) -- | edges attached to the given node attachedEdges ∷ (View [Port] n, MonadReader (Graph n) m) ⇒ Node → m [Edge] attachedEdges = liftM nub . inspectNode -- | non-empty set of nodes attached to the given edge attachedNodes ∷ MonadReader (Graph n) m ⇒ Edge → m [Node] attachedNodes = liftM (map Node . Set.elems) . readEdge -- | amount of ports the given hyperedge is connected to edgeCardinality ∷ (View [Port] n, MonadReader (Graph n) m) ⇒ Edge → m Int edgeCardinality e = liftM (length . filter (e ≡) . concat) (mapM inspectNode =<< attachedNodes e) -- | list of nodes that are connected to the given node, not including the node itself neighbours ∷ (View [Port] n, MonadReader (Graph n) m) ⇒ Node → m [Node] neighbours n@(Node i) = do is ← liftM Set.unions $ mapM readEdge =<< inspectNode n return $ map Node $ Set.elems $ Set.delete i is -- | list of nodes that are connected to the given node, including the node itself relatives ∷ (View [Port] n, MonadReader (Graph n) m) ⇒ Node → m [Node] relatives n@(Node i) = do is ← liftM Set.unions $ mapM readEdge =<< inspectNode n return $ map Node $ Set.elems is -- | nodes connected to given port of the specified node, not including the node itself adverseNodes ∷ MonadReader (Graph n) m ⇒ Node → Port → m [Node] adverseNodes (Node n) p = liftM (map Node . Set.elems . Set.delete n) (readEdge p) -- | whether two nodes are connected connected ∷ (View [Port] n, MonadReader (Graph n) m) ⇒ Node → Node → m Bool connected n1 n2 = liftM (n2 ∈) (relatives n2) -- | whether the given ports features a dangling edge free ∷ (View [Port] n, MonadReader (Graph n) m) ⇒ Port → m Bool free p = do c ← edgeCardinality p return (c ≡ 1) -- | Map node-relative enquiry over the nodes of the graph. withNodes ∷ MonadReader (Graph n) m ⇒ (Node → m a) → m [a] withNodes p = mapM p =<< readNodeList