Question

I cant figure out why I get two different results but I’m sure it has to do with IO, which I am beginning to hate!

For example:

  ghci> x <- readFile "foo.txt"
  ghci> let y = read x :: [Int]
  ghci> :t y
  y :: [Int]

Now when I create that file and do the same thing it comes out as IO [Int] ?

foo.txt is a txt file containing only this: 12345

Someone that can explain this to me? As I’m about to snap it!

Thanks for any insight!

Answer 1

Read about ghci. To quote

The syntax of a statement accepted at the GHCi prompt is exactly the same as the syntax of a statement in a Haskell do expression. However, there’s no monad overloading here: statements typed at the prompt must be in the IO monad.

Basically you are inside the IO Monad when you are writing anything in ghci.