~ readme ~

         .ooo
          'OOOo
      ~ p ooOOOo tion ~
          .OOO
           oO      %% a little
             Oo    fast language.
            'O
             `
            (o)
        ___/ /
       /`    \
      /v^  `  ,
     (...v/v^/
      \../::/
       \/::/

p2 is a she. She is a perl5 and possible perl6/nqp backend, based on why the luck stiff's potion. See README.potion.md why potion is exciting. Homepage: http://perl11.com/p2/

Command	Time
parrot example/fib.pir 28	0m1.746s
perl example/fib.pl 28	0m0.439s
p2 -B example/fib.p2 28	0m0.177s
potion example/fib.pn 28	0m0.013s
p2 example/fib.p2 28	0m0.013s
perl example/fib.p2 28	0m0.196s
raku example/fib.p6 28	0m0.569s
p2 example/fib.p6 28	0m0.018s
parrot example/fib.pir 40	3m36.447s
perl example/fib.pl 40	2m19.752s
p2 -B example/fib.p2 40	1m1.940s
potion example/fib.pn 40	0m3.063s
p2 example/fib.p2 40	0m3.105s
raku example/fib.p6 40	1m29.872s
p2 example/fib.p6 40	0m3.086s

For most small examples comparable performance to lua and C. For bigger examples optimizable via static types/early binding.

Its exciting points for perl folks are:

• Radically simplified and functional core.

• Should parse most of perl5, just some XS and B tricks not.

• Signatures, fast mop, types, native threads, call-replacing macros for perl5.

• No worries about pseudo-scientific discussions, project management, performance bugs and feature deadlocks. Leaving the slack behind.

• A lightweight generational GC, based on Basile Starynkevitch's work on Qish, with ~4ms per GC on average with < 100MB heaps. http://starynkevitch.net/Basile/qishintro.html The compiler will add hooks for objects leaving scope and add DESTROY method calls if they are visible at compile-time. Run-time created DESTROY methods will not be automatically called (yet).

• Using most of Damian Conway's p5i recommendations: i.e. classes are immutable and final by default. See http://web.archive.org/web/20040207072905/http://www.yetanother.org/damian/Perl5+i/

• libp2 is usable as a fast backend for nqp/perl6, but parsing and supporting p6 natively without going through nqp and the rakudo bootstrapping process should be easier and faster. Tokuhiro Matsuno already wrote a p6 parser, pvip.

• Native and fast calling convention, no XS stack args on the heap. XS is replaced by extern (dynamic ffi), and/or shared libraries with normal function calls into the vm.

• Just-in-time compilation for x86, x86-64 and ppc done. arm later.

• Intermediate bytecode format and VM. Load and dump code. Decent speed and cross-architecture. Heavily based on Lua's VM.

• int, str, num are objects, you can optionally type all args and lexical variables. In fact everything is an object as in parrot, even the parsed AST, the vm state.

• Sized arrays are non-autovivifying and initialized with undef, resp. if typed 0, 0.0, "".

  my $a[3]; print $a[3]    # compile-time error: array out of bounds
  my int $i[3]; print $a[2]  # 0
  my num $n[3]; print $n[2]  # 0.0
  my str $s[3]; print $a[2]  # ""

• A new pragma no magic applies to all visible objects in scope.

  {
    no magic;
    use Config;
    print $Config{'ccflags'};
  }
  # compile-time error: Invalid use of tie with no magic

  use

  {
    no magic;
    use Config ();
    print $Config::Config{'ccflags'};
  }

  instead.

• p6model: via scoped mixins, :multi, roles. Like Moose, just better and roughly estimated 800x faster. No multiple inheritance yet, @ISA == 1. Only one parent, depending on another parent, rather multiple mixin compositions.

• ~~ match works because all data are typed objects. A destructuring-bind alike new match operator which matches structures (list, trees, hashes of hashes) against structures, values and types.

• Bootstrapped "id" object model, based on Ian Piumarta's soda languages. This means everything in the language, including object allocation, parser, compiler and interpreter state are part of the object model. (See COPYING for citations.) In fact all objects and classes are closures, which simplifies scoping, and makes p2/potion a functional vm.

• parsers are scoped and run-time loadable for ffi, p6, and other languages.

• Interpreter is thread-safe and reentrant. This should facilitate parallel interpreters initialized in a threadpool.

• Small core. Under 10kloc. Install sloccount and run: make sloc.

• Reified AST and bytecode structures. This is very important to me. By giving access to the parser and compiler, it allows people to target other platforms, write compilers, debuggers, code analysis tools and even fully bootstrapped VMs. I'm not as concerned about the Potion VM being fully bootstrapped, especially as it is tied into the JIT so closely.

• Memory-efficient classes. Stored like C structs. (Although the method lookup table can be used like a hash for storing arbitrary data.)

• The JIT is also used to speed up some other bottlenecks. For example, instance variable and method lookup tables are compiled into machine code.

• Fast asynchronous IO via libuv

However, some warnings:

• Ints cannot hold pointers and need to be boxed. This should be transparent though. Use WeakRefs for pointers.

• Strings are immutable (like Lua) and byte arrays are used for I/O buffers. All strings and symbols are utf8 internally. Identifiers in the potion, p5 and p6 grammars are checked against Unicode XID_Start/XID_Continue, and warned about per the TR39 security profile (mixed scripts, confusables, as in cperl, rcc, java and rust) via libu8ident (core/unicode.c).

• Limited platform support for coroutines. This affects exceptions.

• No regular expression bindings yet (pcre or sregex)

• No OS threads yet.

• No signal handling yet.

• The compiler is mostly good enough, as in lua, but there are no tradional compiler optimizations yet. We'd might need to add constant folding and propagation, simple local basic block optimizations, peephole optimizations, loop optimizations, tracking side-effects. And tailcalls are not yet detected.

• No type checks, bounds-check elimination and type optimizations yet.

~ building and installing ~

make
make install

Look inside the file called INSTALL.md for options.

To debug the interpreter (gdb sessions, the AST and bytecode dumps, how globals, mixins and control keywords work, the threading model) see doc/INTERNALS.md.

~ feverish and fond thankyous ~

why the lucky stiff left the ruby community. potion was his last public project. It's a work of great art and mastership. I could not think of anything better. I think it is better than Go, if potion would have had added auto-threads and channels.

Rob Pike for Go, and the parrot community for parrot.

Larry Wall for perl5. We miss his leadership and technical excellence. Without him nothing got done, and if something was done it was wrong. Besides defined-or, which left Tom Christiansen behind.

why the lucky stiff thanks:

why is gravely indebted to Basile Starynkevitch, who fielded questions about his garbage collector. why favors French hackers to an extreme (Xavier Leroy, Nicolas Cannasse, Guy Decoux, Mathieu Bochard to name only a portion of those he admires) and is very glad to represent their influence in Potion's garbage collector.

Matz, for answering why's questions about conservative GC and for encouraging him so much. Potion's stack scanning code and some of the object model come from Ruby.

Steve Dekorte for the Io language, libgarbagecollector and libcoroutine -- He referred frequently to all of them in sorting out what he wanted.

Of course, Mauricio Fernandez for his inspiring programming journal housed at http://eigenclass.org/R2/ and for works derived throughout the course of it -- extprot most of all. Many of my thoughts about language internals (object repr, GC, etc.) are informed by him.

Ian Piumarta for peg/leg. We use a re-entrant customized version of it, but the original library is sheer minimalist parsing amazement.

Final appreciations to Jonathan Wright and William Morgan who pitched in, back in the wee hours of Potion's history. Thanks.

~ license ~

See COPYING for legal information. potion is MIT licensed, which lets you do anything you want with this. p2 and perl6 code is ARTISTIC 2 licensed.