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Module Generic_util_obj

module Generic_util_obj: sig .. end
Functions that directly manipulate the memory representation of ocaml values.

Unless marked otherwise, all functions are safe in the sense that they will not cause a segfault. Please report a bug otherwise.


General functions on caml values


val dup_if_block : Obj.t -> Obj.t
Duplicate a block. The identity on integers

Value representation


type tag =
| Constructor of int
| Lazy
| Closure
| Object
| Infix
| Forward
| Abstract
| String
| Double
| Double_array
| Custom
| Unaligned
| Out_of_heap
| Int
Each ocaml values is associated to a tag, an integer. We provide a variant type Generic_util_obj.tag that is more descriptive.
type obj =
| Int of int
| Block of tag * Obj.t array
Variant type reflecting the implementation of ocaml values, they are either an immediate (integer) value or a block with a tag and a number of fields.
val view : Obj.t -> obj
A view on the memory representation of values.
val tag_view : int -> tag
Converts the result of Obj.tag to a more descriptive type.
Raises Invalid_argument when the integer is not one of the known tag.

Variant types


type con_id = bool * int
Type of constructor identifiers, the result type of function Generic_util_obj.con_id
val con_id : 'a -> con_id
Discriminates each constructor of a variant datatype by returning a distinct pair of (bool,int) for each of them. The boolean is true iff the constructor is constant. Two constructors of different types might have the same con_id. The function doesn't discriminate the constructors of extensible variants.
val is_con : Obj.t -> bool
True if the value could be a value of a non-polymorphic variant type: the value must be either an immediate value or a block whose tag is within the range of constructor tags.
val gsize : Obj.t -> int
Either the size of a block (the number of its fields) or 0 for an immediate value.
val fields_all2 : (Obj.t -> Obj.t -> bool) -> Obj.t -> Obj.t -> bool
fields_all p x y holds iff x and y are both be block of the same size, and the binary predicate p holds for all their fields: 

fields_all2 p x y  <==>  forall i . p (x.i, y.i)

val listify : Obj.t -> Obj.t
Given a obj of type (x0,...xn), computes a nested product (x0, (x1, (..., xn) ...))
Raises Invalid_argument if the argument is not a tuple (a block with tag zero).

Extensible variants

Helpers for working with the memory representation of extensible variants.
val is_ext_con : Obj.t -> bool
Returns whether the object is a constructor of an extensible variant.
val ext_con : Obj.t -> Obj.t
Extracts the constructor of an extensible variant (the from a value which may be a constructor application.
Raises Invalid_argument when the value is not an extensible variant.

Property. is_ext_con (ext_con x)

val ext_con_name : Obj.t -> string
Returns the constructor name of an extensible variant.
Raises Invalid_argument when the value is not an extensile variant.
val ext_con_id : Obj.t -> int
Returns the unique object identifier associated with an extensible constructor.
Raises Invalid_argument when the value is not an extensile variant.

Polymorphic variants


val poly_hash : 'a -> int
Returns the hash value associated with a constructor of a polymorphic variant
Raises Invalid_argument if the argument is not a polymorphic variant

Custom blocks


val custom_identifier : 'a -> string
Returns the identifier of a custom block, or the empty string if the block isn't a custom one.