Ocaml: How can I return the first element of a list and after that remove it from the list? :  I'm new in Functional Programming and I'm trying to learn a little bit of Ocaml and I tried to use **List.hd** and **List.tl** for this task:

`let takeCard fst deck =   
    fst = List.hd deck   
    List.tl deck`  
  

'List.hd' takes two arguments but I don't understand why.   
Please, help ! :'(