]> On Sat, Jan 10, 2009 at 12:34:22PM +0100, Antoine Delignat-Lavaud wrote: > In Ocaml, the program > let el = [] in if List.length el > 0 then (List.hd el)+(int_of_string > (List.hd el)) else 0 ;; > yields not type error and returns 0 despite the use of el as both an int > list and a string list. > > Thus, I am wondering why does value restriction not apply to the empty > list in Ocaml. I don't think it's possible to do a cast with the empty > list (it is empty after all) but I don't see any benefit in doing so. It's a strange one ... when the if statement appears as a toplevel statement, OCaml infers the type 'a list for the list: # let el = [] ;; val el : 'a list = [] # if List.length el > 0 then (List.hd el)+(int_of_string (List.hd el)) else 0;; - : int = 0 # el ;; - : 'a list = [] But the same if statement within a function definition causes an error: # let f el = if List.length el > 0 then (List.hd el)+(int_of_string (List.hd el)) else 0;; ^^^^^^^^^^ This expression has type int but is here used with type string Rich. -- Richard Jones Red Hat