Parser and AST for the Nit language

The parser ans the AST are mostly used by all tools.

The `parser` is the tool that transform source-files into abstract syntax trees (AST) (see `parser_nodes`)
While the AST is a higher abstraction than blob of text, the AST is still limited and represents only *What the programmer says*.

Classes of nodes of the AST starts with the letter `A` (for most things, eg. `AClassdef`) or `T` (for token eg. `TId`), there is no real reason except historical that might be solved with a new parser.

Variable names of the AST usually starts with `n` (for node). This is also historical but some names with a `a` (to mimic the class name) remains.

## SableCC

Most files in this directory are generated from a grammar for sablecc3 ( http://www.sablecc.org ).
In order to generate nit parser, you need the alternate SableCC3 generator ( http://www.mare.ee/indrek/sablecc/ ).

## Contents

* fact_parser.pl: Script used to factorize parser.nit
* Makefile: Update grammar and generate .nit files
* nit.sablecc3xx: Extended sablecc3 grammar (see prescc.pl)
* prescc.pl: Program to transform an extended sablecc3 to a standard one
* parser_nodes.nit: token and nodes classes hierarchy used by the parser and the lexer
* tables.nit, tables_nit.h: Interfaces to access the tables needed by the parser and the lexer
* xss/*.xss: alternate SableCC3 template files for the Nit language


The following are generated but present to avoid the need of sablecc3:

* lexer.nit: generated lexer
* parser.nit: generated parser
* parser_prod.nit: All production with generated visit methods
* tables_nit.c: The tables needed by the parser and the lexer
* parser_abs.nit: Raw generated token and nodes classes used to maintain coherence of parser_nodes.nit


Other temp files produced by the Makefile:

* .nit.sablecc3: Sablecc3 grammar after processing
* .nit.sablecc3.dump: Dump of the grammar to improve sablecc3 multiple runs
* .parser-nofact.nit: The parser generated by SableCC3 before factorization by fact_parser.pl