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|
----------------------------------------------------------------------
-- |
-- Module : Graph
-- Maintainer : BB
-- Stability : (stable)
-- Portability : (portable)
--
-- > CVS $Date: 2005/11/10 16:43:44 $
-- > CVS $Author: bringert $
-- > CVS $Revision: 1.2 $
--
-- A simple graph module.
-----------------------------------------------------------------------------
module GF.Speech.Graph ( Graph(..), Node, Edge, Incoming, Outgoing
, newGraph, nodes, edges
, nmap, emap, newNode, newNodes, newEdge, newEdges
, incoming, outgoing, getOutgoing
, getFrom, getTo, getLabel
, reverseGraph, renameNodes
) where
import GF.Data.Utilities
import Data.List
data Graph n a b = Graph [n] [Node n a] [Edge n b]
deriving (Eq,Show)
type Node n a = (n,a)
type Edge n b = (n,n,b)
type Incoming n a b = [(Node n a,[Edge n b])]
type Outgoing n a b = [(Node n a,[Edge n b])]
newGraph :: [n] -> Graph n a b
newGraph ns = Graph ns [] []
nodes :: Graph n a b -> [Node n a]
nodes (Graph _ ns _) = ns
edges :: Graph n a b -> [Edge n b]
edges (Graph _ _ es) = es
-- | Map a function over the node label.s
nmap :: (a -> c) -> Graph n a b -> Graph n c b
nmap f (Graph c ns es) = Graph c [(n,f l) | (n,l) <- ns] es
-- | Map a function over the edge labels.
emap :: (b -> c) -> Graph n a b -> Graph n a c
emap f (Graph c ns es) = Graph c ns [(x,y,f l) | (x,y,l) <- es]
newNode :: a -> Graph n a b -> (Graph n a b,n)
newNode l (Graph (c:cs) ns es) = (Graph cs ((c,l):ns) es, c)
newNodes :: [a] -> Graph n a b -> (Graph n a b,[Node n a])
newNodes ls (Graph cs ns es) = (Graph cs' (ns'++ns) es, ns')
where (xs,cs') = splitAt (length ls) cs
ns' = zip xs ls
newEdge :: Edge n b -> Graph n a b -> Graph n a b
newEdge e (Graph c ns es) = Graph c ns (e:es)
newEdges :: [Edge n b] -> Graph n a b -> Graph n a b
newEdges es' (Graph c ns es) = Graph c ns (es'++es)
-- | Get a list of all nodes and their incoming edges.
incoming :: Ord n => Graph n a b -> Incoming n a b
incoming = groupEdgesBy getTo
-- | Get a list of all nodes and their outgoing edges.
outgoing :: Ord n => Graph n a b -> Outgoing n a b
outgoing = groupEdgesBy getFrom
-- | From a list of outgoing edges, get all edges
-- starting at a given node.
getOutgoing :: Eq n => Outgoing n a b -> n -> [Edge n b]
getOutgoing out x = head [ es | ((y,_),es) <- out, x == y ]
groupEdgesBy :: (Ord n) => (Edge n b -> n) -> Graph n a b -> [(Node n a,[Edge n b])]
groupEdgesBy h (Graph _ ns es) =
snd $ mapAccumL f (sortBy (compareBy h) es) (sortBy (compareBy fst) ns)
where f es' v@(n,_) = let (nes,es'') = span ((==n) . h) es' in (es'',(v,nes))
getFrom :: Edge n b -> n
getFrom (f,_,_) = f
getTo :: Edge n b -> n
getTo (_,t,_) = t
getLabel :: Edge n b -> b
getLabel (_,_,l) = l
reverseGraph :: Graph n a b -> Graph n a b
reverseGraph (Graph c ns es) = Graph c ns [ (t,f,l) | (f,t,l) <- es ]
-- | Re-name the nodes in the graph.
renameNodes :: (n -> m) -- ^ renaming function
-> [m] -- ^ infinite supply of fresh node names, to
-- use when adding nodes in the future.
-> Graph n a b -> Graph m a b
renameNodes newName c (Graph _ ns es) = Graph c ns' es'
where ns' = [ (newName n,x) | (n,x) <- ns ]
es' = [ (newName f, newName t, l) | (f,t,l) <- es]
|
