package atd

To support the generation of annotations for types that are created during the monomorphization process, a mapping must be kept connecting the monomorphic type name to the original polymorphic one, including its original number of parameters.

This table is only used in producing those annotations to support the Atdgen command line option -o-name-overlap. It can probably be ignored for most uses of expand_module_body.

Monomorphization of type expressions.

• parameter prefix

  prefix to use for new type names. Default is "_".

• parameter keep_poly

  return definitions for the parametrized types. Default is false.

• parameter debug

  keep meaningful but non ATD-compliant names for new type names. Default is false.

  The goal is to inline each parametrized type definition as much as possible, allowing code generators to create more efficient code directly:

    type ('a, 'b) t = [ Foo of 'a | Bar of 'b ]
    type int_t = (int, int) t

  becomes:

    type int_t = _1
    type _1 = [ Foo of int | Bar of int ]

  A secondary goal is to factor out type subexpressions in order for the code generators to produce less code:

    type x = \{ x : int list }
    type y = \{ y : int list option }

  becomes:

    type x = \{ x : _1 }
    type y = \{ y : _2 }
    type _1 = int list   (* `int list' now occurs only once *)
    type _2 = _1 option

  By default, only parameterless type definitions are returned. The keep_poly option allows to return parametrized type definitions as well.

  Input:

    type 'a abs = abstract
    type int_abs = int abs
    type 'a tree = [ Leaf of 'a | Node of ('a tree * 'a tree) ]
    type t = int tree
    type x = [ Foo | Bar ] tree

  Output (pseudo-syntax where quoted strings indicate unique type identifiers):

    type "int abs" = int abs
    type int_abs = "int abs"
  
    type 'a tree = [ Leaf of 'a | Node of ('a tree * 'a tree) ]
      (* only if keep_poly = true *)
  
    type "int tree" = [ Leaf of int | Node of ("int tree" * "int tree") ]
    type t = "int tree"
    type "[ Foo | Bar ] tree" =
      [ Leaf of [ Foo | Bar ]
      | Node of ("[ Foo | Bar ] tree" * "[ Foo | Bar ] tree") ]
    type x = "[ Foo | Bar ] tree"