add pagerank

cbits/Structure.chs.c

 #include "IGraph/Internal/Structure.chs.h"
+int __c2hs_wrapped__igraph_pagerank(const igraph_t * graph,
+                                    igraph_pagerank_algo_t algo,
+                                    igraph_vector_t * vector,
+                                    igraph_real_t * value,
+                                    const igraph_vs_t * vids,
+                                    igraph_bool_t directed,
+                                    igraph_real_t damping,
+                                    const igraph_vector_t * weights,
+                                    void * options)
+{
+    return igraph_pagerank(graph,
+                           algo,
+                           vector,
+                           value,
+                           *vids,
+                           directed,
+                           damping,
+                           weights,
+                           options);
+}
 int __c2hs_wrapped__igraph_induced_subgraph(const igraph_t * graph,
                                             igraph_t * res,
                                             const igraph_vs_t * vids,

src/IGraph/Internal/Constants.chs

@@ -5,15 +5,23 @@ import Foreign
 
 #include "cbits/haskelligraph.c"
 
-{#enum igraph_neimode_t as Neimode {underscoreToCase} deriving (Show, Eq) #}
+{#enum igraph_neimode_t as Neimode {underscoreToCase}
+    deriving (Show, Eq) #}
 
-{#enum igraph_edgeorder_type_t as EdgeOrderType {underscoreToCase} deriving (Show, Eq) #}
+{#enum igraph_edgeorder_type_t as EdgeOrderType {underscoreToCase}
+    deriving (Show, Eq) #}
 
-{#enum igraph_spincomm_update_t as SpincommUpdate {underscoreToCase} deriving (Show, Eq) #}
+{#enum igraph_spincomm_update_t as SpincommUpdate {underscoreToCase}
+    deriving (Show, Eq) #}
 
-{#enum igraph_spinglass_implementation_t as SpinglassImplementation {underscoreToCase} deriving (Show, Eq) #}
+{#enum igraph_spinglass_implementation_t as SpinglassImplementation {underscoreToCase}
+    deriving (Show, Eq) #}
 
-{#enum igraph_attribute_elemtype_t as AttributeElemtype {underscoreToCase} deriving (Show, Eq) #}
+{#enum igraph_attribute_elemtype_t as AttributeElemtype {underscoreToCase}
+    deriving (Show, Eq) #}
 
 {#enum igraph_subgraph_implementation_t as SubgraphImplementation {underscoreToCase}
-       deriving (Show, Read, Eq) #}
+    deriving (Show, Read, Eq) #}
+
+{#enum igraph_pagerank_algo_t as PagerankAlgo {underscoreToCase}
+    deriving (Show, Read, Eq) #}

src/IGraph/Internal/Structure.chs

@@ -38,3 +38,13 @@ import Foreign.C.Types
                                          , `Bool'
                                          , `VectorPtr'
                                          , `ArpackOptPtr' } -> `Int' #}
+
+{#fun igraph_pagerank as ^ { `IGraphPtr'
+                           , `PagerankAlgo'
+                           , `VectorPtr'
+                           , id `Ptr CDouble'
+                           , %`IGraphVsPtr'
+                           , `Bool'
+                           , `Double'
+                           , `VectorPtr'
+                           , id `Ptr ()' } -> `Int' #}

src/IGraph/Structure.hs

@@ -3,6 +3,7 @@ module IGraph.Structure
     , closeness
     , betweenness
     , eigenvectorCentrality
+    , pagerank
     ) where
 
 import Control.Monad
@@ -78,3 +79,19 @@ eigenvectorCentrality gr ws = unsafePerformIO $ do
     arparck <- igraphArpackNew
     igraphEigenvectorCentrality (_graph gr) vptr nullPtr True True ws' arparck
     vectorPtrToList vptr
+
+-- | Google's PageRank
+pagerank :: Graph d
+         => LGraph d v e
+         -> Maybe [Double]
+         -> Double  -- ^ damping factor, usually around 0.85
+         -> [Double]
+pagerank gr ws d = unsafePerformIO $ alloca $ \p -> do
+    vptr <- igraphVectorNew 0
+    vsptr <- igraphVsAll
+    ws' <- case ws of
+        Just w -> listToVector w
+        _ -> liftM VectorPtr $ newForeignPtr_ $ castPtr nullPtr
+    igraphPagerank (_graph gr) IgraphPagerankAlgoPrpack vptr p vsptr
+        (isDirected gr) d ws' nullPtr
+    vectorPtrToList vptr