Non-deterministic die roll

Main.idr

module Main

import Effect.Random
import Effect.StdIO
import Effect.System

getSeed : { [SYSTEM] } Eff Integer
getSeed = do case index' 1 !getArgs of
                  Nothing => pure $ cast !time
                  Just t => pure $ cast t

computeAndDisplay : Integer -> { [RND, STDIO] } Eff ()
computeAndDisplay seed = do srand seed
                            x <- rndInt 1 7
                            putStrLn $ show x ++ " (seed " ++ show seed ++ ")"

rollDie : { [RND, STDIO, SYSTEM] } Eff ()
rollDie = do computeAndDisplay !getSeed

main : IO ()
main = run rollDie