===== Request for Comments: Replace Bison based parser with Lemon =====

  * **Version:** 0.2
  * **Date:** 2010-07-13
  * **Author:** Etienne Kneuss, Felipe Pena
  * **Status:** Abandoned

=== Abstract ===
The current parser is bison based. The plan (initially proposed as a GSoC idea) is to replace it with Lemon, which is thread-safe and reentrant.

This task can be divided into two main parts:

  * rewrite zend_language_parser.y into a syntax Lemon understands.
  * generate the template for an engine/re2c integration.

Writing the syntax file is pretty straight-forward, though some additional rules need to be implemented in order to reproduce those bison "mid-rule actions", which isn't supported by Lemon.
It might be a good idea to rethink some of the rules' names along the way.

=== News from the front ===

The rewrite is finished, but we still need to figure out some slight performance issues.

An effect of the yacc->lemon switch is that tokens are no longer named in error messages.

Before:

Unexpected T_IF

Now:

Unexpected 'if'


=== Updates ===
2008-03-25 : Initial draft.
2010-07-13 : Updates.