Dot suffix on type variable

Learning
1

I’m looking through the Resto code and I’m seeing the following line:

pp: 'a. 'a Encoding.t -> Format.formatter -> string -> unit ;


I’m searching through the OCaml documentation and cannot find what that trailing . in 'a. means.

2

https://caml.inria.fr/pub/docs/manual-ocaml/types.html

Search for “poly-typeexpr”. It’s an explicitly-polymorphic type.

3

The manual chapter on polymorphism explains some of the use of those annotations in recursion or higher-rank polymorphic functions.

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