Stdlib.Type(3)                   OCaml library                  Stdlib.Type(3)

NAME
       Stdlib.Type - no description

Module
       Module   Stdlib.Type

Documentation
       Module Type
        : (module Stdlib__Type)









   Type equality witness
       type (_, _) eq =
        | Equal : ('a, 'a) eq


       The purpose of eq is to represent type equalities that may not
       otherwise be known by the type checker (e.g. because they may depend on
       dynamic data).

       A value of type (a, b) eq represents the fact that types a and b are
       equal.

       If one has a value eq : (a, b) eq that proves types a and b are equal,
       one can use it to convert a value of type a to a value of type b by
       pattern matching on Equal :
             let cast (type a) (type b) (Equal : (a, b) Type.eq) (a : a) : b = a


       At runtime, this function simply returns its second argument unchanged.




   Type identifiers
       module Id : sig end


       Type identifiers.

       A type identifier is a value that denotes a type. Given two type
       identifiers, they can be tested for Type.Id.provably_equal to prove
       they denote the same type. Note that:


       -Unequal identifiers do not imply unequal types: a given type can be
       denoted by more than one identifier.

       -Type identifiers can be marshalled, but they get a new, distinct,
       identity on unmarshalling, so the equalities are lost.

       See an Type.Id.example of use.



OCamldoc                          2024-02-29                    Stdlib.Type(3)