pX/Common/README - fglock

This is lrep - the Lister Rubbish Eclectic Pathologically  (Juerd++)
 or: Least Recursively Expressed Perl (TimToady++)

It is an experimental implementation of:
- a parser engine (iterator_engine.pl)
- a Perl6 'rule' parser and perl5 emitter (p6rule.pl)
- a 'Perl6' parser and perl5 emitter (p6compiler.pl)
- a Perl6 'grammar' grammar (p6prelude.pl)

Tests: (paste this in the command line to run all tests)
  perl iterator_engine.t
  perl p6compiler.pl p6sample.pl
  perl p6compiler.pl p6compiler.p6t

  pugs iterator_engine.p6t

Special thanks for the brainstorming sessions in #perl6:
- putter
- audreyt
- TimToady 
- pmurias

Bootstrapping:
ok - core rule engine - backtracking, function composition - in Perl 5
ok - Perl 6 rules in Perl 5 - reuse to write itself
ok - Perl 6 grammar in Perl 5 - reuse to write itself
ok - Perl 6 to Perl 5 translator (parse p6, emit p5) - reuse to write 
     itself
   - Perl 6 compiler written in p6
- see also: TASKS

Perl6 Grammar implemented:
  
  grammar  <name>;
  rule     <name> {...}   
    -- 'return block' is source filtered
    -- operators are being implemented on demand
  rule     <name> rx:perl5{...}
  say print warn die <list>;
  my our local    <var>;
    -- untested
  {...}
  eval( '1+1', :lang<perl5> );
  sub <name> {...}   
    -- need more work on fixity and precedence, parameter binding
  push unshift       
    -- bootstrapped with source filter
  macro <name> ( *@args ) is parsed ( /.../ ) {...}   
    -- argument binding is source filtered
  if (cond) {block}
    -- macro needs to be rewritten with anon-subs
    
Rules Grammar implemented:

 . ? * + *? +? ??
 \char <ws> <word> literal
 $variable @variable
 <'literal'>
 [] 
 ()     
 <subrule>
 <namespace::subrule>
 <?subrule>
 <!subrule>
 |
 <@var>    - special-cased for array-of-rule (but not Rule|Str)
 {code}    - non-capturing closure
           - bootstrapped with source-filter
           - $/ doesn't work yet
 { return code } - capturing closure
           - bootstrapped with source filter
           - $/ works
 $var := (capture)  - capture aliasing
 $<> $/<>  - special variables can't be used inside a match, yet
 $/ 
 $<0> $<1>

- implemented but untested:
 <$var>

- not implemented:
 $/<0> $/<1>
 $/0 $/1
 $0 $1
 <"literal">
 ^ ^^ $ $$
 <unicode-class> <+unicode-class> <+unicode-class+unicode-class>
 <&var> 
 <%var>
 **{n..m}
 : :: :::   (commit)
 $var := [non-capture]
 $var := <rule>
 <(closure-assertion)> <{code-returns-rule}>
 <<character-class>> <[character-class]>
 :flag :flag() :flag[]
 lookahead lookbehind
 #comment\n
 \x0a \o123 ...
 <?ws>  -- optional whitespace ???
 &    
 <!abc> -- is this !<abc> or !abc ?
 \n \N

- not sure if specified:
 'literal' "literal"
 <!n,m>  -- <!{n..m}> ???

See also:

- some existing Perl6 'grammar' grammars:
  ../../Grammars/rx_grammar.pm
  http://svn.perl.org/parrot/trunk/compilers/pge/P6Rule.grammar