Polymorphism in OCaml - ad hoc,parametric, inclusion/subtyping

Question

I am having a problem understanding the different types of polymorphism, specifically in regards to OCaml. I understand that polymorphism allows for multiple types in OCaml den

Answer 1

ident is polymorphous :

# let ident x = x;;
val ident : 'a -> 'a = 

# ident 1;;
- : int = 1
# ident "ok";;
- : string = "ok"
# ident [];;
- : 'a list = []
# ident List.length;;
- : '_a list -> int = 
# ident ident;;
- : '_a -> '_a = 

fold also :

# open List;;
# fold_left (+) 0 [1;2;3];;
- : int = 6
# fold_left (^) "" ["1";"2";"3"];;
- : string = "123"
# fold_left (fun a (x,y)  -> a+x*y) 0 [(1,2);(3,4);(5,6)];;
- : int = 44