Ocaml pattern matching/ member of function

Question

The following function is trying to match a (int * stmt list) list (where stmt is just a type defined elsewhere) and return a stmt list.

 let rec findinlist (r: int) (l1: (int * stmt list) list ) (l2: stmt list) =   
      (match l1 with 
      | [] -> l2
      | h:: _ when h= (r,s) -> s
      | _ :: t -> findinlist r t l2
      )

First off this gives me an unbound value s error but how would I go about accomplishing this?

Théo Winterhalter Théo Winterhalter · Accepted Answer · 2015-05-16T18:08:41

When you use when it is not another pattern matching which would bind s. It is just a boolean test that expects a boolean (like an if statement).

Maybe you want something like:

let rec findinlist (r: int) (l1: (int * stmt list) list ) (l2: stmt list) =   
  (match l1 with 
  | [] -> l2
  | (r',s):: _ when r' = r -> s
  | _ :: t -> findinlist r t l2
  )

Ocaml pattern matching/ member of function

1 Answers