How to get the ASCII value of a character in Haskell?

How to get the ASCII value of a character in Haskell? I've tried to use the ord function in GHCi, based on what I read here bug the the error message:

Not in scope: `ord'

For example:

GHCi, version 6.12.1: http:/开发者_如何学Go/www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
Prelude> ord 'a'

<interactive>:1:0: Not in scope: `ord'
Prelude>

What am I doing wrong?

As Travis Brown indicated in a comment, you have to import the ord function from the module Data.Char:

import Data.Char (ord)

main = print (ord 'a')

Only the Prelude module is loaded by default, all other modules have to be imported explicitly.

You can also use fromEnum. (defined in Enum class, from Prelude.)

Prelude> :i Char
data Char = GHC.Types.C# GHC.Prim.Char#     -- Defined in `GHC.Types'
instance Enum Char -- Defined in `GHC.Enum'
instance Eq Char -- Defined in `GHC.Classes'
...

So you can use fromEnum and toEnum, which uses the ASCII code as the Int value.

Prelude> fromEnum 'A'
65
Prelude> fromEnum 'a'
97
Prelude> toEnum 9 :: Char
'\t'
Prelude> toEnum 100 :: Char
'd'