[PPT] - Ka w a Other languages on JVM Compiling Dynamic Languages PowerPoint Presentation

SLIDE 1 Ka w a Compiling Dynamic Languages to the Ja v a VM P er Bothner bothnercygnusc

m
Cygn

us Solutions UsenixF r e enix

Dr

aft version June

Other

languages

n

JVM Ja v a can b e though t

f

as t w

dieren

t things Ja v a as a programming language

b

jectorien ted syn tax similar to CC Ja v a as a mac hineen vironmen t libraries

p
rtable

b yteco des run virtual mac hine Need for

ther

languages to coexist in the Ja v a en vironmen t Highlev el scripting languages esp ecially useful Can use extensiv e Ja v a libraries and p

rtable

b yteco des Benet from Ja v a

ptimization

eorts Man y examples NetRexx Tcl Ada

June
Implemen

tation Strategies In terpreter written in Ja v a Go

d

resp

nsiv

eness Slo w execution time T ranslate to Ja v a source P

r

resp

nsiv

eness F ast execution time T ranslate to Ja v a b yteco de Go

d

resp

nsiv

eness F ast execution time Ka w a do es the last T ranslating Sc heme directly to b yteco des is m uc h faster Required for in teractiv e resp

nse

in readev alprin t lo

p

Byteco des are more general b yteco des ha v e goto whic h is not in Ja v a language June

Ev

al

Immediate

execution Scripting languages ha v e eval T ak e a command t yp ed in teractiv ely

r

constructed

n

the y

and

immediately execute it A batc h translator do es not supp

rt

eval w ell Ka w a compiles directly to inmemory b yteco des so is highly resp

nsiv

e Uses a simple in terpreter for simple expressions for ev en faster resp

nse

June

SLIDE 2 Compilation F ron tend Sc heme source

read
list

form

analysis
R

ECMAScript

lexer
tok

en stream

parser
Expression

June

Compilation

Bac kend Expression

R
ptimization
co

de generation

ClassType
R
writeToArray
in

ternal arra y

writeToFile
class

le

R
R

zip arc hiv e

ClassLoader
Running

co de June

Loading

a Sc heme source le Read expressions un til EOF

normally

yields a sequence

f

PairWithPosition lists W rap expressions in a dumm y noargumen t lambda The analysis phase do es macro expansion resolv es lexical bindings Could do

ptimizations

Result is a LambdaExp expression

b

ject Compile to in ternal b yte arra ys con taining b yteco des and class denitions Uses the same format as Ja v a class les Use a ClassLoader to con v ert b yte arra ys to loaded classes Apply the result whic h ev aluates toplev el expressions June

Expressions

Abstract Expression class represen ts languageindep enden t partially pro cessed expressions IfExp

conditional

expression ApplyExp

application

call LambdaExp

anon

ymous pro cedures LetExp

blo

c k with lexical bindings QuoteExp

literal

constan t ReferenceExp

v

ariable reference ErrorExp

syn

tax error seen

compile

metho d compiles the expression in to b yteco de instructions eval is

nly

used to ev aluate simple expressions in teractiv ely

June

SLIDE 3 Co de Generation public abstract class Expression

public

abstract void compileCompilatio n state Target target

A

Compilation manages the state for a compilation unit and manages

ne
r

more gnubytecodeClass Ty pe

b

jects

ne

for eac h generated class le T

compile

an Expression in v

k

e its compile metho d This generates b yteco des to ev aluate the Expression Calls compile recursiv ely for subexpressions A Target sp ecies where to lea v e the result June

The

bytecode P ac k age The gnubytecode pac k age is an ecien t in termediatelev el library for w

rking

with Ja v a class les Co de generation reading writing prin ting disassem bling ClassType

Information

ab

ut

a class as a whole CpoolEntry abstract

A

slot in the constan t p

l

Variable

Lo

cal v ariable Field Attribute abstract

Used

for miscellaneous info Method

Handles

metho ds and b yteco de instructions CodeAttr

A

Methods b yteco de instructions

CodeAttr

has man y mediumlev el metho ds for generating b yteco de instructions F

r

example c

de

attremitPushInti Generates co de to push int literal i

n

JVM stac k June

Calling

Ja v a metho ds Ka w a mak es it con v enien t to call Ja v a metho ds form Sc heme define charupcase char primitivestati cm et hod javalangCharac te r toUpperCase char char char Con v erts Sc heme c haracter v alue to Ja v a primitiv e char calls toUpperCase metho d in javalangCharac ter

and

con v erts result bac k Compiler can inline call to kno wn primitiv e metho d Otherwise Ja v a reection feature is used Similar access to arra y elemen ts and

b

ject elds June

Sc

heme vs Ja v a Sc heme and Ja v a are v ery dieren t kinds

f

languages Sc heme is dynamically t yp ed while Ja v a is statically t yp ed Ja v a is an

b

jectorien ted language Sc heme is a nonpure functional language Pro cedures are rstclass

b

jects lexical scoping requires closures Sc heme denes arithmetic

n

a tree

f

n um b er t yp es Ja v a normally uses ra w mac hinelev el n um b ers Ho w should w e map Sc heme constructs in to Ja v a constructs June

SLIDE 4 Dynamic T yp es Ja v a lik e Smalltalk and unlik e C has a ro

ted

inheritance graph All classes are deriv ed from the class Object whic h is an alias for javalangObject Sc heme and ECMAScript ha v e v ariable declarations but without t yp e sp ecications hence all Sc heme v alues b elong to some subclass

f

Object Some latitude when to use standard builtin Ja v a classes for Sc heme v alues

r

write

ur
wn

June

Ob

jects and V alues Sc heme b

leans

are represen ted using Ja v a Booleans Sym b

ls

are represen ted using in terned Ja v a Strings Sc heme lists v ectors and strings use new classes in a Sequence colections hierarc h y

June
Sequences

abstract class Sequence class Vector extends Sequence Used for Sc heme v ectors class List extends Sequence ListEmpty

new

List

Empty

list class Pair extends List Has car and cdr elds class PairWithPosition extends Pair A Pair with linen um b er information June

Num

b ers gnumath pac k age implemen ts Sc heme n um b ers and more F

rms

a coheren t class hierarc h y

Pro

vides inniteprecision rationals Complex n um b ers pro vided Has quan tities with units and dimensions June

SLIDE 5 Pro cedures public abstract class Procedure

public

abstract Object applyNObject args

A

primitiv e pro cedure is written in Ja v a as a subclass

f

Procedure Eg

denes

applyN to add argumen ts A Sc heme function is compiled in to a sub class

f

Procedure with the Sc heme b

dy

compiled in to b

dy
f

applyN Allo cating instance

f

a Procedure subclass creates Sc heme pro cedure v alue Nested pro cedure has a eld for the static con text inherited lexical en vironmen t A closure is an instance

f

suc h a class June

T

ailcalls Sc heme language requires tailcalleliminati

n

whic h is a generalization

f

tailrecursionelimination CALL F follo w ed b y RETURN should b e same as GOTO F Ie curren t frame m ust b e p

pp

ed b efore CALL to a v

id

stac k gro wth Allo ws iteration and state mac hines to b e expressed using recursion Best handled with suitable calling con v en tion whic h is not p

rtable

in Ja v a Ka w a implemen ts tailrecursionelimination

nly

If compiler sees a call to the curren t function it replaces it b y a goto General tailcalleliminatio n will b e implemen ted using a new heapbased calling con v en tion can coexist with the curren t faster calling con v en tion June

Con

tin uations Continuations pro vide a w a y to capture the curren t stac k en vironmen t They can b e used to implemen t new con trol structures coroutines bac ktrac king exception handling and more Can b e implemen ted b y cop ying the stac k

but

this requires assem blylev el co de Ka w a implemen ts limited con tin uations sucien t to implemen t catc hthro w and exception handling It uses the Ja v a exception handling mec hanism F ull supp

rt

will b e added based

n

the new tailcall con v en tion June

Other

languages Most

f

the Ka w a is indep enden t

f

Sc heme The same tec hniques and most

f

the co de could b e reused to implemen t

ther

languages esp ecially dynamically t yp ed

nes

suc h as Tcl Rexx Smalltalk APL

New

languages ma y require new data t yp es

just

write the appropriate Ja v a classes Most languages require their

wn

parser This w

uld

translate text in to Expressions Eac h language has a dieren t standard en vironmen t con taining predened v alues t yp es and functions June

SLIDE 6 ECMAScript ECMA standard no

for

the core

f

Ja v aScript V ery dynamic

b

jectbased language with protot yp e inheritance but no classes Lexer and parser written Most predened functions and

b

jects missing Generates Expression and compiles to Ja v a b yteco des June

DSSSL

and SGML Industry migrating to SGML for do cumen t storage and manipulation HTML is an instance

f

SGML XML is simplied SGML DSSSL is the ISO standard language for sp ecifying st yle and pro cessing

f

SGML DSSSL is basically standard Sc heme with no sideeects plus some extensions plus lots

f

standard classes for manipulating text

w

etc The

riginal

preCygn us Ka w a w as written to pro cess DSSSL Ka w a implemen ts some

f

the DSSSL extensions DSSSL seems b e the cause

f

renew ed in terest in Sc heme and Ka w a June

Status

and F uture w

rk

Ka w a is used for a n um b er

f

commercial and academic pro jects and has a mem b er mailing list Ka w a is still b eing activ ely dev elop ed and enhanced Plans include Implemen t missing features

f

standard Sc heme R

RS

Finish ECMAScript implemen tation Implemen t Emacs Lisp core Pla y with an arra y language Design a graphics in terface Add a mo dule system Supp

rt
ptional

t yp e declarations and lo cal t yp e inference Supp

rt

using ra w Ja v a data t yp es in Sc heme

June
Fine

prin t Not a Cygn us pro duct No connection with T ekT

ls

Ja v a IDE

f

the same name Home page httpwwwcygnu s com

bot

hn er ka wa ht ml June