Question

Possible Duplicate:
Two fields of two records have same label in OCaml

In Ocaml 3.12.0, is it necessary that any labels of a record have globally unique names?

type foo = { a : int; b : char; }
# type bar = {a : int; b : string};;
type bar = { a : int; b : string; }
# {a=3; b='a'};;
  {a=3; b='a'};;
Error: This expression has type char but an expression was expected of type
         string

I guess if the record is created anonymously, the only way for the compiler to know which type I’m referring to is the record names. Does declaring bar hide foo?

Answer 1

No, record labels don’t have to be globally unique. But they have to be unique in module level.

Declaring bar doesn’t hide foo; therefore, type inference is broken when refering to b field.

You can easily create submodules and use module names to distinguish between records with the same label:

module Foo = struct
  type foo = {a: int; b: char}
end

module Bar = struct
  type bar = {a: int; b: string}
end

let f = {Foo.a = 3; b = 'a'} (* Note that we only need to use module name once *)
let b = {Bar.a = 3; b = "a"}