Ast\_iterator(3) OCaml library Ast\_iterator(3)

# [NAME](#NAME)

Ast\_iterator - Ast\_iterator.iterator enables AST inspection using open recursion.

# [Module](#Module)

Module Ast\_iterator

# [Documentation](#Documentation)

Module **Ast\_iterator**  
: **sig end**

**Ast\_iterator.iterator** enables AST inspection using open recursion. A typical mapper would be based on **Ast\_iterator.default\_iterator** , a trivial iterator, and will fall back on it for handling the syntax it does not modify.

Warning: this module is unstable and part of **Compiler\_libs** .

## [A generic Parsetree iterator](#A_generic_Parsetree_iterator)

*type iterator* = {  
attribute : **iterator -> Parsetree.attribute -> unit** ;  
attributes : **iterator -> Parsetree.attribute list -> unit** ;  
binding\_op : **iterator -> Parsetree.binding\_op -> unit** ;  
case : **iterator -> Parsetree.case -> unit** ;  
cases : **iterator -> Parsetree.case list -> unit** ;  
class\_declaration : **iterator -> Parsetree.class\_declaration -> unit** ;  
class\_description : **iterator -> Parsetree.class\_description -> unit** ;  
class\_expr : **iterator -> Parsetree.class\_expr -> unit** ;  
class\_field : **iterator -> Parsetree.class\_field -> unit** ;  
class\_signature : **iterator -> Parsetree.class\_signature -> unit** ;  
class\_structure : **iterator -> Parsetree.class\_structure -> unit** ;  
class\_type : **iterator -> Parsetree.class\_type -> unit** ;  
class\_type\_declaration : **iterator -> Parsetree.class\_type\_declaration -> unit** ;  
class\_type\_field : **iterator -> Parsetree.class\_type\_field -> unit** ;  
constructor\_declaration : **iterator -> Parsetree.constructor\_declaration -> unit** ;  
directive\_argument : **iterator -> Parsetree.directive\_argument -> unit** ;  
expr : **iterator -> Parsetree.expression -> unit** ;  
extension : **iterator -> Parsetree.extension -> unit** ;  
extension\_constructor : **iterator -> Parsetree.extension\_constructor -> unit** ;  
include\_declaration : **iterator -> Parsetree.include\_declaration -> unit** ;  
include\_description : **iterator -> Parsetree.include\_description -> unit** ;  
label\_declaration : **iterator -> Parsetree.label\_declaration -> unit** ;  
location : **iterator -> Location.t -> unit** ;  
module\_binding : **iterator -> Parsetree.module\_binding -> unit** ;  
module\_declaration : **iterator -> Parsetree.module\_declaration -> unit** ;  
module\_substitution : **iterator -> Parsetree.module\_substitution -> unit** ;  
module\_expr : **iterator -> Parsetree.module\_expr -> unit** ;  
module\_type : **iterator -> Parsetree.module\_type -> unit** ;  
module\_type\_declaration : **iterator -> Parsetree.module\_type\_declaration -> unit** ;  
open\_declaration : **iterator -> Parsetree.open\_declaration -> unit** ;  
open\_description : **iterator -> Parsetree.open\_description -> unit** ;  
package\_type : **iterator -> Parsetree.package\_type -> unit** ;  
pat : **iterator -> Parsetree.pattern -> unit** ;  
payload : **iterator -> Parsetree.payload -> unit** ;  
signature : **iterator -> Parsetree.signature -> unit** ;  
signature\_item : **iterator -> Parsetree.signature\_item -> unit** ;  
structure : **iterator -> Parsetree.structure -> unit** ;  
structure\_item : **iterator -> Parsetree.structure\_item -> unit** ;  
toplevel\_directive : **iterator -> Parsetree.toplevel\_directive -> unit** ;  
toplevel\_phrase : **iterator -> Parsetree.toplevel\_phrase -> unit** ;  
typ : **iterator -> Parsetree.core\_type -> unit** ;  
row\_field : **iterator -> Parsetree.row\_field -> unit** ;  
object\_field : **iterator -> Parsetree.object\_field -> unit** ;  
type\_declaration : **iterator -> Parsetree.type\_declaration -> unit** ;  
type\_extension : **iterator -> Parsetree.type\_extension -> unit** ;  
type\_exception : **iterator -> Parsetree.type\_exception -> unit** ;  
type\_kind : **iterator -> Parsetree.type\_kind -> unit** ;  
value\_binding : **iterator -> Parsetree.value\_binding -> unit** ;  
value\_description : **iterator -> Parsetree.value\_description -> unit** ;  
with\_constraint : **iterator -> Parsetree.with\_constraint -> unit** ;  
}

A **iterator** record implements one "method" per syntactic category, using an open recursion style: each method takes as its first argument the iterator to be applied to children in the syntax tree.

*val default\_iterator* : **iterator**

A default iterator, which implements a "do not do anything" mapping.

2026-09-04 OCamldoc

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Document: Ast_iterator(3o) from ocaml 5.5.1-r0 (Chainguard OS)
Source: https://github.com/ocaml/ocaml