package metaquot

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OCaml syntax extension for quoting code


Dune Dependency






metaquot allows to quote OCaml code.

Published: 29 Feb 2020


metaquot: OCaml syntax extension for quoting code

metaquot is a PPX rewriter that provides several extensions for quoting OCaml code in expressions, à la ppxtools.ppx_metaquot and ppxlib.metaquot. In comparison to these libraries, metaquot is built by meta-programmation over the Parsetree module (thanks to metapp) and is meant to be trivial to update for future versions of OCaml (on the other hand, metaquot only builds AST for the current version of OCaml: you may use helpers provided by Ast_helper or Metapp to manipulate the AST in a version-independent manner).

metaquot can be used with dune by using the preprocess field.

  (preprocess (pps metaquot.ppx))

The following extensions are provided.

Quotation Type
[%expr ...] Parsetree.expression
[%pat? ...] Parsetree.pattern
[%type: ...] Parsetree.core_type
[%sig: ...] Parsetree.signature
[%sigi: ...] Parsetree.signature_item
[%str ...] Parsetree.structure
[%stri ...] Parsetree.structure_item

The produced AST uses !Ast_helper.default_loc as location: you may change the location with Ast_helper.with_default_loc.

Moreover, in quoted code, the following extensions allow to evaluate and insert expressions or patterns (anti-quotations).

Anti-quotation Type
[%e ...] Parsetree.expression
[%p ...] Parsetree.pattern
[%t ...] Parsetree.core_type
[%m ...] Parsetree.module_type or Parsetree.module_expr
[%i ...] Parsetree.signature_item or Parsetree.structure_item

In addition to the syntax extension, the metaquot package provides the Metaquot module, which contains lifters: the Metaquot.Exp module lifts to expressions and Metaquot.Pat lifts to patterns. For instance, Metaquot.Exp.pattern : Parsetree.pattern -> Parsetree.expression is a function that returns an OCaml expression that builds the AST corresponding to the given pattern.

Dependencies (6)

  1. metapp >= "0.1.0" & < "0.2.0"
  2. dune >= "1.11.0"
  3. ocamlfind >= "1.8.1"
  4. ocaml-migrate-parsetree >= "1.5.0" & < "2.0.0"
  5. stdcompat >= "12"
  6. ocaml >= "4.03.0" & < "4.11.0"

Dev Dependencies


Used by (2)

  1. pattern = "0.2.0"
  2. traverse < "0.2.0"




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