[Haskell-cafe] Silly question: accessing a slot in a data type

[Fernando Rodriguez]

Hi,

I'm writing a very simple address book. I defined the follwoing types for 
Contact and AddressBook:

type Name= String
type PhoneNumber= Integer

data Contact = Contact {name :: Name, phone:: PhoneNumber} deriving Show

-- The addressBook is a lista of Contacts
data AddressBook= AddressBook [Contact] deriving Show

-- Create a test one
ag = Agenda [Contact "BillG" 618965332, Contact "Linus" 5897458]

I wan't to write a function to search for a given phone by name and return 
a Maybe PhoneNumber.  I know how to do this recursively on a "raw" list, 
but how do I access the list inside AddressBook? Also, how do I represent 
an AddressBook with an empty list and one with data on its list for my pattern 
matching?

Thanks!