Calling function in ocaml with ref list


I have ref list and I am writing this function -
let atrr = ref [(1,2);(3,4)]

let rec findAttributeList attrList x =
match !attrList with
[] -> false
|(a,b)::tl-> if a = x then false else true; findAttributeList (tl) x;;

Getting error while calling findAttributeList-

Error: This expression has type ('a * 'b) list
but an expression was expected of type ('a * 'b) list ref

Here, tl has type ('a * 'b) list, your function expects a ('a * 'b) list ref because you wrote !attrList, so you should write findAttributeList (ref tl) x.

You should probably dereference the list before feeding it to the function. Also, you have two bugs on your if expression: the function will always iterate and never return true.

How should I do that? I am very new to Ocaml. I will appreciate your help.

let atrr = ref [(1,2);(3,4)]

let rec find l x =
    match l with
    | [] -> false
    |(a,_)::tl -> if a = x then true else find tl x
find !attr