Dear Jacques:

I was reading the manual of chap4, it says

tag-spec-full	::=	`tag-name [ `of` typexpr ] { `&` typexpr }
	∣	typexpr

I don't follow the (&) operation here, it means intersection types ?

I managed to make a working example:

type 'a ab = [< `a|`b] as 'a ;;

type 'a ac = 'a constraint 'a = [< `a | `c ]

type ('a,'b) m = [< `m of 'a ab & 'a ac ] as 'b;;

let u : ('a,'b) m = `m `a;;

(* val u : ([ `a ], [ `m of [ `a ] ab ]) m = `m `a *)

But still don't understand its use case, can you explain a bit about this?

Many thanks

Regards

-- Bob