istribution (from @Statistics.Distribution.Exponential@)
-- 
-- > λ> mwc $ listOf 10 (exponential 0.2)
-- > [ 5.713524665694821,1.7774315204594584,2.434017573227628
-- > , 5.463202731505528,0.5403008025455847,14.346316301765576
-- > , 7.380393612391503,24.800854500680032,0.8731076703020924
-- > , 6.1661076502236645 ]
exponential :: PrimMonad m
            => Double -- ^ lambda (scale) parameter
            -> RandT m Double
exponential = continuous . E.exponential

-- | Exponential 
exponential :: PrimMonad m
            => Double -- ^ lambda (scale) parameter
            -> RandT m Double
exponential = continuous . E.exponential
exponential = continuous . E.exponential