[Haskell-cafe] St. Petersburg Game

[Ketil Malde]

manolo at austrohungaro.com writes:

> increment b = b + 1

This is also called 'succ' (for successor).

> main =  do	let b = 0
> 		let c = randomRIO (1,2)
> 		until (c == 1)	increment b
>             	return b

> ERROR "StPetersburg.hs":8 - Type error in application
> *** Expression     : until (c == 1) increment b
> *** Term           : c == 1
> *** Type           : Bool
> *** Does not match : Int -> Bool

  Prelude> :t until
  until :: (a -> Bool) -> (a -> a) -> a -> a

So until wants a function from a something to a boolean, but you are
giving it (c==1) which is just a boolean.

More generally, I think you should solve this in a more functional
style, perhaps using randomRs to get a list of coin tosses, and take
what you need from that.

-k
-- 
If I haven't seen further, it is by standing in the footprints of giants