change API for IGraph.Layout

src/IGraph/Layout.hs

 module IGraph.Layout
-    ( kamadaKawai
+    ( getLayout
+    , LayoutOpt(..)
+    , LayoutMethod(..)
     ) where
 
 import Foreign (nullPtr)
@@ -15,21 +17,44 @@ import IGraph.Internal.Data
 data LayoutOpt = LayoutOpt
     { _seed :: Maybe [(Double, Double)]
     , _nIter :: Int
-    } deriving (Show)
+    , _method :: LayoutMethod
+    , _sigma :: (Int -> Double)  -- ^ [KamadaKawai] the base standard deviation of position change proposals
+    , _startTemp :: Double  -- ^ [KamadaKawai] the initial temperature for the annealing
+    , _coolFact :: Double  -- ^ [KamadaKawai] the cooling factor for the simulated annealing
+    , _kkConst :: (Int -> Double)  -- ^ [KamadaKawai] The Kamada-Kawai vertex attraction constant
+    }
 
 instance Default LayoutOpt where
     def = LayoutOpt
         { _seed = Nothing
         , _nIter = 10000
+        , _method = KamadaKawai
+        , _sigma = \x -> fromIntegral x / 4
+        , _startTemp = 10
+        , _coolFact = 0.99
+        , _kkConst = \x -> fromIntegral $ x^2
         }
 
-kamadaKawai :: Graph d => LGraph d v e -> Double -> Double -> Double -> Double -> LayoutOpt -> [(Double, Double)]
-kamadaKawai gr sigma initemp coolexp kkconst opt = unsafePerformIO $ do
+data LayoutMethod = KamadaKawai
+
+getLayout :: Graph d => LGraph d v e -> LayoutOpt -> [(Double, Double)]
+getLayout gr opt = unsafePerformIO $ do
     mptr <- mat
-    igraphLayoutKamadaKawai (_graph gr) mptr (_nIter opt) sigma initemp coolexp kkconst useSeed nullPtr nullPtr nullPtr nullPtr
+
+    case _method opt of
+        KamadaKawai -> igraphLayoutKamadaKawai gptr mptr iters s initemp coolexp
+                       kkconst useSeed nullPtr nullPtr nullPtr nullPtr
+
     [x, y] <- matrixPtrToColumnLists mptr
     return $ zip x y
   where
+    n = nNodes gr
+    gptr = _graph gr
+    iters = _nIter opt
+    s = _sigma opt n
+    initemp = _startTemp opt
+    coolexp = _coolFact opt
+    kkconst = _kkConst opt n
     (useSeed, mat) = case _seed opt of
         Just xs -> if length xs /= nNodes gr
                       then error "Seed error: incorrect size"

src/IGraph/Read.hs

 module IGraph.Read
     ( readAdjMatrix
+    , fromAdjMatrix
     , readAdjMatrixWeighted
     ) where
 
@@ -14,18 +15,21 @@ readDouble = fst . fromJust . readSigned readExponential
 {-# INLINE readDouble #-}
 
 readAdjMatrix :: Graph d => FilePath -> IO (LGraph d B.ByteString ())
-readAdjMatrix fl = do
-    c <- B.readFile fl
-    let (header:xs) = B.lines c
+readAdjMatrix = fmap fromAdjMatrix . B.readFile
+
+fromAdjMatrix :: Graph d => B.ByteString -> LGraph d B.ByteString ()
+fromAdjMatrix bs =
+    let (header:xs) = B.lines bs
         mat = map (map readDouble . B.words) xs
         es = fst $ unzip $ filter f $ zip [ (i,j) | i <- [0..nrow-1], j <- [0..nrow-1] ] $ concat mat
         nrow = length mat
         ncol = length $ head mat
-    if nrow /= ncol
-       then error "nrow != ncol"
-       else return $ mkGraph (nrow, Just $ B.words header) (es, Nothing)
+    in if nrow /= ncol
+         then error "fromAdjMatrix: nrow != ncol"
+         else mkGraph (nrow, Just $ B.words header) (es, Nothing)
   where
     f ((i,j),v) = i < j && v /= 0
+{-# INLINE fromAdjMatrix #-}
 
 readAdjMatrixWeighted :: Graph d => FilePath -> IO (LGraph d B.ByteString Double)
 readAdjMatrixWeighted fl = do