This works:
Prelude System.Random> do { randomRIO (1,6) >>= (\x -> putStrLn $ "Value = " ++
show x) }
Value = 5
So does this:
Prelude System.Random> do { x <- randomRIO (1,6); putStrLn $ "Value = " ++ show
x }
Value = 2
But not this:
1 import Control.Monad
2 import System.Random
3
4 foo :: IO ()
5 foo = do
6 x <- randomRIO (1,6)
7 putStrLn $ "Value = " ++ show x
foo.hs:6:18:
Ambiguous type variable `t' in the constraints:
`Num t' arising from the literal `1' at foo.hs:6:18
`Random t' arising from a use of `randomRIO' at foo.hs:6:7-21
Probable fix: add a type signature that fixes these type variable(s)
Failed, modules loaded: none.
Prelude System.Random>
Or this:
1 import Control.Monad
2 import System.Random
3
4 foo :: IO ()
5 foo = randomRIO (1,6) >>= (\x -> putStrLn $ "Value = " ++ show x)
foo.hs:5:17:
Ambiguous type variable `t' in the constraints:
`Num t' arising from the literal `1' at foo.hs:5:17
`Random t' arising from a use of `randomRIO' at foo.hs:5:6-20
Probable fix: add a type signature that fixes these type variable(s)
Failed, modules loaded: none.
How to fix?
Michael
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