Description

The concrete-syntax package provides =parse-cs, a generic program for parsing programs with embedded concrete syntax. The program is parameterized with meta-data indicating components for various aspects such as parsing, exploding, desugaring, and pretty-printing. The meta data can be specified in a .meta file specific for a program to be parsed, or it can be associated with an extension and registered in an XTC repository.

For example, the following is the contents of pl.meta, the meta-data for Prolog programs with embedded syntax. The assumption (in this example) is that syntax embeddings use a standard (ToTerm^?) convention for indicating the boundary between meta- and object-syntax.

  Meta([
    Syntax("Prolog"),
    ParseTable("Prolog.tbl"),
    Explode("prolog-explode"),
    PrettyPrintTable("Prolog-pretty.pp.af")
  ])

This information can be overridden in a file specific .meta file with the same extension. For example, the following indicates an embedding of ABIR in Prolog and a specific desugaring tool for this format:

  Meta([
    Syntax("PrologABIR"),
    PostExplodeDesugar("abir-in-prolog-implode")
  ])

It overrides the syntax component, and adds a desugaring component.

In order to define such meta-data for a whole class of programs, it can be defined in a meta file associated with a new extension. For example, the following is the contents plabir.meta, which defines all meta-data for preprocessing Prolog with embedded ABIR in files with extension .plabir.

  Meta([
    Syntax("PrologABIR"),
    Explode("prolog-explode"),
    PostExplodeDesugar("abir-in-prolog-implode"),
    PrettyPrintTable("Prolog-pretty.pp.af")
  ])

Concrete Syntax Tools

Parse-cs is the only tool provided by the package at the moment. Other tools that might be provided in the future include:

• embed-syntax : combines two syntax definitions embedding one in the other by generating quotation productions and variable schemas according to a standard schema which might be adapted.

• gen-explode : a generic explosion transformation for embeddings that can be expressed locally (term-like API in host language) and generically

Implementation

Browse the implementation in the subversion repository:

• https://svn.cs.uu.nl:12443/repos/StrategoXT/trunk/StrategoXT/concrete-syntax/

The package is available in the daily distribution^? of StrategoXT and will be available in StrategoRelease094.

The instantiation of the tool for Prolog is available in the PrologTools package.