.ooo
 'OOOo
 ~ p ooOOOo tion ~
 .OOO
 oO %% a little
 Oo fast language.
 'O
 `
 (o)
 ___/ / 
 /` \ 
 /v^ ` ,
 (...v/v^/
 \../::/
 \/::/ 
 ~ potion ~
 Potion is an object- and mixin-oriented (traits)
 language.
 Its exciting points are:
 * Just-in-time compilation to x86 and x86-64
 machine code function pointers. This means
 she's a speedy one. Who integrates very
 well with C extensions.
 The JIT is turned on by default and is
 considered the primary mode of operation.
 * Intermediate bytecode format and VM. Load
 and dump code. Decent speed and cross-
 architecture. Heavily based on Lua's VM.
 * A lightweight generational GC, based on
 Basile Starynkevitch's work on Qish.
 <http://starynkevitch.net/Basile/qishintro.html>
 * Bootstrapped "id" object model, based on
 Ian Piumarta's soda languages. This means
 everything in the language, including
 object allocation and interpreter state
 are part of the object model.
 (See COPYING for citations.)
 * Interpreter is thread-safe and reentrant.
 I hope this will facilitate coroutines,
 parallel interpreters and sandboxing.
 * Small. Under 10kloc. Right now we're like
 6,000 or something. 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 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.
 However, some warnings:
 * Strings are immutable (like Lua) and byte
 arrays are used for I/O buffers.
 * No floating point support yet.
 * No error handling. I'm wary of just tossing
 in exceptions and feeling rather uninspired
 on the matter. Let's hear from you.
 ~ a whiff of potion ~
 5 times: "Odelay!" print.
 Or,
 add = (x, y): x + y.
 add(2, 4) string print
 Or,
 hello =
 "(x): ('hello ', x) print." eval
 hello ('world')
 ~ building and installing ~
 $ make
 Look inside the file called INSTALL for options.
 ~ how it transpired ~
 This isn't supposed to happen!
 I started playing with Lua's internals and reading
 stuff by Ian Piumarta and Nicolas Cannasse. And I,
 well... I don't know how this happened!
 Turns out making a language is a lovely old time,
 you should try it. If you keep it small, fit the
 VM and the parser and the stdlib all into 10k
 lines, then it's no sweat.
 To be fair, I'd been tinkering with the parser
 for years, though.
 ~ the potion pledge ~
 EVERYTHING IS AN OBJECT.
 However, OBJECTS AREN'T EVERYTHING.
 (And, incidentally, everything is a function.)
 ~ items to understand ~
 1. A traditional object is a tuple of data
 and methods: (D, M).
 
 D is kept in the object itself.
 M is kept in classes.
 2. In Potion, objects are just D.
 
 3. Every object has an M.
 4. But M can be altered, swapped,
 added to, removed from, whatever.
 5. Objects do not have classes.
 The M is a mixin, a collection
 of methods.
 Example: all strings have a "length"
 method. This method comes with Potion.
 It's in the String mixin.
 6. You can swap out mixins for the span
 of a single source file.
 Example: you could give all strings a
 "backwards" method. But just for the
 code inside your test.pn script.
 7. You can re-mix for the span of a
 single closure.
 To sum up:
 EVERYTHING IS AN OBJECT.
 EVEN MIXINS ARE OBJECTS.
 AND, OF COURSE, CLOSURES ARE OBJECTS.
 However, OBJECTS AREN'T EVERYTHING.
 THEY ARE USELESS WITHOUT MIXINS.
 ~ unique ideas (to be implemented) ~
 Potion does have a few unique features
 underway.
 * It is two languages in one.
 The language itself is objects and closures.
 Number add = (x): self + x.
 But it also includes a data language.
 app = [window (width=200, height=400)
 [button "OK", button "Cancel"]]
 
 The code and data languages can be interleaved
 over and over again. In a way, I'm trying to find
 a middle ground between s-expressions and stuff like
 E4X. I like that s-expressions are a very light data
 syntax, but I like that E4X clearly looks like data.
 When s-expressions appear in Lisp code, they look
 like code. I think it is nice to distinguish the two.
 * Deeply nested blocks can be closed quickly.
 I don't like significant whitespace, personally.
 But I don't like end end end end.
 say = (phrase):
 10 times (i):
 20 times (j):
 phrase print
 _say
 The closing "_ say" ends the block saved to "say" var.
 Normally, blocks are closed with a period. In this case
 we'd need three periods, which looks strange.
 say = ():
 10 times:
 20 times:
 "Odelay!" print
 ...
 If you prefer, you can give it some space. Or you can
 use a variable name introduced by the block,
 say = (phrase):
 10 times (i):
 20 times (j):
 phrase print
 _ phrase
 say = (phrase):
 10 times (i):
 20 times (j):
 phrase print
 _ i
 .
 Maybe it all looks strange. I don't know. I'm just trying
 things out, okay?
 * Elimination of line noise.
 I avoid @, #, ,ドル %, {}.
 Stick with ., |, (), [], =, !, ?. Easier on the eyes.
 These are common punctuations in English.
 * I try to defer to English when it comes to punctuation rules.
 Period means "end". (In other langs it means "method call".)
 Comma breaks up statements.
 Space between messages gives a noun-verb feeling.
 window open (width=400, height=500)
 * Named block args.
 (1, 2, 3) map (item=x, index=i): i display, x + 1.
 ~ feverish and fond thankyous ~
 I am gravely indebted to Basile Starynkevitch, who fielded my
 questions about his garbage collector. I favor French hackers
 to an extreme (Xavier Leroy, Nicolas Cannasse, Guy Decoux,
 Mathieu Bochard to name only a portion of those I admire) and
 am very glad to represent their influence in Potion's garbage
 collector.
 Matz, for answering my questions about conservative GC and
 for encouraging me 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 -- I referred frequently to all of them in
 sorting out what I 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. I use a re-entrant custom 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.
 Tanks.
 ~ license ~
 See COPYING for legal information. It's an MIT license,
 which lets you do anything you want with this. I'm hoping
 that makes it very nice for folks who want to embed a little
 Potion in their app!