module Data.Graph.Generation where
import Control.Monad (replicateM)
import Data.List (foldl')
import System.Random
import Data.Graph.Types
newtype Probability = P Float deriving (Eq, Ord, Show)
probability :: Float -> Probability
probability v | v >= 1 = P 1 | v <= 0 = P 0 | otherwise = P v
erdosRenyiIO :: Graph g => Int -> Probability -> IO (g Int ())
erdosRenyiIO n (P p) = go [1..n] p empty
where
go :: Graph g => [Int] -> Float -> g Int () -> IO (g Int ())
go [] _ g = return g
go (v:vs) pv g = do
rnds <- randomRs (0.0, 1.0) <$> newStdGen
let vs' = zip rnds vs
go vs pv $! (foldl' (putV pv v) g vs')
putV :: Graph g => Float -> Int -> g Int () -> (Float, Int) -> g Int ()
putV pv v g (p', v') | p' < pv = insertEdgePair (v, v') g | otherwise = g
randomMatIO :: Int -> IO [[Int]]
randomMatIO n = replicateM n randRow
where randRow = replicateM n (randomRIO (0,1)) :: IO [Int]