histfill :: IO Double -> TH1D ->  IO () 
histfill gen hist = do 
  x <- gen
  fill1 hist x
  return () 
histfill :: IO Double -> TH1D ->  IO ()
histfill gen hist = do 
  x <- gen
  fill1 hist x
  return () 
histfill gen hist = do 
  x <- gen
  fill1 hist x
  return () 