Perlito5-in-JavaScript

Command line

execute a Perl script

$ nodejs perlito5.js -Isrc5/lib -e ' say "hello, World!" '

compile a Perl script to a JavaScript file with -Cjs

$ nodejs perlito5.js -Isrc5/lib -Cjs -e ' say "hello, World!" ' > out.js

$ nodejs out.js

enable debugging mode with -JS DEBUG. This prints the JavaScript code just before it is executed
```
$ nodejs perlito5.js -Isrc5/lib -JS DEBUG t5-js/op/wantarray.t
```

Perlito5-in-JavaScript - what works

Subroutines, anonymous subroutines, prototypes, namespaces. main, CORE and CORE::GLOBAL.
Scalar, Hash, Array, Code should work the same as in perl.
Objects should work the same as in perl.
Scalar vs. List context, wantarray().
Variables. my, our, local, state. Most special variables. Most variable declarations.
Most control structures. next, last, redo, continue and labels. goto &subr. goto LABEL - some use patterns work.
Most string, numeric, array, hash operators.
Some I/O operators.
Some regex operators.
Tie array.
AUTOLOAD.

Perlito5-in-JavaScript differences from "perl"

reference to scalar doesn't work properly. The reference points to a copy of the value
~~ smartmatch is not implemented
sleep is not implemented in the browser. Perlito5 in node.js implements sleep using an npm module.
Perlito5 in the browser doesn't implement many of the perl I/O operators; Perlito5 in node.js should implement most of the I/O operators.
JavaScript doesn't implement reference counting; DESTROY will not work; weaken() will be a no-op.
Overload is not implemented yet.
XS is not supported. Use JS::inline instead.
Variable aliasing is not implemented yet; modifying $_ or $_[0] doesn't change the original variable.
utf8 is not implemented yet.
Regex is missing some features
Control structures are partially implemented;
- goto LABEL - some use patterns work.
- goto &sub works, but tail call is not implemented yet.
- "computed goto" is not implemented
- given is not implemented.
String pos() is not implemented yet.
Signals are not implemented yet.
BEGIN blocks are mostly implemented.
Typeglobs are partially implemented.
tie() is partially implemented.
String increment partially implemented - array and hash lookups; not in scalars.
runtime error messages often do not include the right line number in the Perl code
form and formline are not implemented yet.

Calling Perl subroutines from JavaScript

var myfun = p5cget( "My::Module", "mysub" );

Export a Perl subroutine to a JavaScript variable
var myobj = p5cget( "My::Module", "mysub" )( [ arg1, arg2 ], null );

Call a Perl subroutine. The "null" in the end means calling in scalar context.
var myobj = p5call( "Statistics::Distributions", "new", [ arg1, arg2 ], null );

Method call.

Calling JavaScript methods from Perl

The Perl AUTOLOAD mechanism is used to fallback to JavaScript: if a method doesn't exist in Perl, it will retry in native JavaScript.

$ node perlito5.js -I src5/lib -e ' console->log(123); console->log( Math->max(2,3) ); '
123
3

$ node perlito5.js -I src5/lib -e '  Math->max(); print Math->max(9,2,5), "\n";  print Math->max->apply(undef,[9,2,3,7]), "\n"; '
9
9

Calling constructors using new:

$ node perlito5.js -I src5/lib -e ' my $r = RegExp->new("abc", "g"); print $r->toString(), " ", $r->test("xabcx"), " ", $r->lastIndex, "\n";'
/abc/g 1 4

Alternately, use the JS::inline() method:

$ node perlito5.js -I src5/lib -e ' JS::inline(" console.log(123); "); '

TODO - nice to have - assignment to object attribute like:

document->getElementById("print-result")->value = "abc";

Internals

Perlito5 JavaScript Data model Overview

Perlito5 compiler globals

context: system-wide; shared by all modules

    $Perlito5::CORE_PROTO = { 'CORE::join' => '$@' }

- hashref with subroutine-full-name to prototype mappings in the CORE package only

    $Perlito5::PROTO = { 'main::mysub' => undef }

- hashref with subroutine-full-name to prototype mappings

context: module-wide

    $Perlito5::PKG_NAME = "main"

- the current package name (unescaped string)

context: subroutine-wide

    $Perlito5::THROW = 1

- boolean value; tracks if the current subroutine needs to catch a javascript "throw" as a return-value

context: lexical block

    $Perlito5::VAR = [ { '$_'    => { decl => 'our', namespace => 'main' } ]

- arrayref-of-hashes with variable-short-names to (declaration type, namespace) mappings

method call

lookup the method in the _class_ attribute; follow the class hierarchy through @ISA until the UNIVERSAL base class.
do a native call on the method.
the argument list is the named array List__ (that is, @_).
additional arguments can be used to pass out-of-band data, such as: caller(), wantarray()
the invocant is the first argument. this is not used.

subroutine call

lookup the subroutine in the current namespace; follow the hierarchy until the CORE base class.
do a native method call.
the argument list is the named array List__ (that is, @_).
additional arguments can be used to pass out-of-band data, such as: caller(), wantarray()
this is not used.

Hash

native {} with perl5-specific getters and setters

Array

native [] with perl5-specific getters and setters

Scalar

native value

Tied containers

javascript object with perl5-specific getters and setters

HashRef

native {} wrapped in a HashRef object

ArrayRef

native [] wrapped in a ArrayRef object

ScalarRef

native value wrapped in a ScalarRef object

CodeRef

native value

Object

one of the reference types, with a _class_ attribute

Class

classes are stored in the CLASS global hash
the _class_ attribute points to the class itself
classes inherit from UNIVERSAL

Namespace

namespaces are stored in the p5pkg global hash
current namespace object is in the PKG variable
Namespace inherits from from CORE::GLOBAL, which inherits from CORE
Namespace is a copy of the Class, but with a different inheritance
Namespace and Class are updated in parallel, both when a sub is declared or when using typeglob assignment

Calling context (wantarray, caller)

TODO
these are the possible compile-time contexts: 'scalar' 'list' 'void' 'runtime' (unknown)

'str' 'bool' 'num'
at run-time the contexts are in wantarray (p5want variable): 1 0 undef

Alias

TODO
using String/Boolean/Number (boxed types) as SCALARs doesn't seem to work

List (eg. subroutine return value)

native []

eval string

the compiler gets the current namespace as an argument
javascript eval() happens at the current runtime lexical context

eval block

...

do block

...

AUTOLOAD

...

my

...

local

...

our

...

JavaScript resources

https://github.com/eriwen/javascript-stacktrace

how to get a stacktrace in browsers

https://github.com/audreyt/pugs/tree/master/perl5/PIL2JS

Pugs Perl6 in javascript

crypt implementation https://github.com/TimDumol/unix-crypt-td-js/blob/master/src/unix-crypt-td.js

Regex

regex extension libraries

See: http://xregexp.com https://github.com/benekastah/empcre
modifiers supported: g i m s x e xx
From http://www.regular-expressions.info/javascript.html

No \A or \Z anchors to match the start or end of the string. Use a caret or dollar instead. Lookbehind is not supported at all. Lookahead is fully supported. No atomic grouping or possessive quantifiers No Unicode support, except for matching single characters with No named capturing groups. Use numbered capturing groups instead. No mode modifiers to set matching options within the regular expression. (Work in progress) No conditionals. No regular expression comments with (?#text)

Cell-based aliasing (TODO)

slow
allows aliasing (rw parameters to functions)
allows tie, because collection access is done through methods
simplifies autovivification
allows lvalue subroutines, such as chop(), chomp(), keys(), pos(), substr(), undef()
allows our
examples:

    v = new Cell();
    v.set(5);
    f(v);   // f gets a copy of the cell; v.set() inside f() modifies the original variable.
    1 + v;  // calls v.valueOf()
    x = v;  // alias (copies the cell); v.set() modifies x.valueOf()
    x.set( v.valueOf() );  // copies the value (doesn't alias)

    h.lookup("x");  // looks up h["x"] for a cell; autovivifies if needed
    v.lookup("x");  // error if the cell in v contains something else than undef or an arrayref

see mp6_Scalar class in src6/lib/Perlito/Python/Runtime.py

Tail call (TODO)

a tail call can be transformed into a loop at the caller:

    sub mysub { goto &other }

can be called:

    ret = new TailCall(mysub);
    do {
        ret = ret.f();
    }
    while (ret instanceof TailCall);

alternately, the loop can be run at the subroutine itself, but this creates other problems
tailcalls same-subroutine tailcalls could execute a redo in the current subroutine.

"js3" virtual machine

"js3" milestones (TODO list)
- timely destruction (depends on reference counting); weaken()
- tie()
- Overload
- variable aliasing ($_[0], for-loop, map)
- make perlito usable for CPAN smoke tests:
  
  node perlito5.js Makefile.PL make test
possible implementation of lexical variables

This allows better control over memory allocation (for example, to implement destructors and aliasing)

    // lexical variables
    function p5env_001 () {};
    var p5env = p5env_001;
    p5env.a = 3;

    function myfun () {
        var p5env_002 = function () {};
        p5env_002.prototype = p5env_001;

        var p5env = new p5env_002();
        p5env.b = 4;
        process.stdout.write( ""  + p5env.a + " " + p5env.b + "\n" );
        p5env.a = 5;
        process.stdout.write( ""  + p5env.a + " " + p5env.b + "\n" );
    }

    myfun();
    process.stdout.write( ""  + p5env.a + " " + p5env.b + "\n" );

    @_ is special:
    $_[n] lvalue can be represented by

    at_env[n][at_var[n]] = ...

subroutine call:

    mysub( [
            env,         "var", // a variable
            env.arr,     0,     // a subscript
            [ 123 ],     0      // a value
        ], context );

lvalue subroutine call:

??? - maybe use 'context' to force return of a settable object

tied containers: Tie::Scalar magic can be implemented with getters/setters in env

    p5env.b = 4;    // call b setter if there is a setter

Tie::Array, Tie::Hash

    p5env.list_b[0] = 4; // ??? - but this works if we use a method to get/set the variable

problem: tie'ing a variable in the outer scope (p5env_001) using defineProperty() would be inherited by the inner scope (p5env_002 in the example above).

workaround: access variables from the outer scope directly, without using inheritance. This can be complicated by statements like { my $v = 0 if $x } which create lexicals dynamically - but the behaviour in this case is undefined anyway.

defineProperty() can be used to provide accessors to non-tied containers:

    Object.defineProperty( Array.prototype, "p5aget", {
        enumerable : false,
        value : function (i) { return this[i] }
    });
    Object.defineProperty( Array.prototype, "p5aset", {
        enumerable : false,
        value : function (i, v) { this[i] = v; return this[i] }
    });

    Object.defineProperty( Object.prototype, "p5hget", {
        enumerable : false,
        value : function (i) { return this[i] }
    });
    Object.defineProperty( Object.prototype, "p5hset", {
        enumerable : false,
        value : function (i, v) { this[i] = v; return this[i] }
    });

    b = [5,6,8];
    b.p5aset(2, 13);
    process.stdout.write( " " + b.p5aget(2) + "\n" );

    h = { x : 4, y : 7 };
    h.p5hset("x", 13);
    process.stdout.write( " " + h.p5hget("x") + "\n" );

Alternative implementation for lvalue @_ and tail calls

  // calling function x()
  // the variables (a,b,c) are lexicals aliased to $_[0], $_[1], $_[2]
  // .mod signals that @_ was modified
  // .at  returns @_
  // .res is the funtion result
  // .tail is a tail-call result flag
  function(){
      r = x([a,b,c], want);
      if (r.mod) { a=r.at[0]; b=r.at[1]; c=r.at[2] };
      while (r.tail) {
          // do tail calls
      }
      return r.res
  }()

Perlito5 JavaScript backend TODO list

Features

create __DATA__

%Perlito5::DATA_SECTION contains the __DATA__ for each package

DESTROY

Try::Tiny uses DESTROY to implement finally() - and it doesn't execute in js:

  $ nodejs perlito5.js -Isrc5/lib -I. -I /usr/local/lib/perl5/site_perl/5.20.0  -e ' use Try::Tiny; try { print "this\n" }; try { die "this" } catch { print "catched\n" } finally { print "done\n" } '
  this
  catched

  $ perl -e ' use Try::Tiny;  try { print "this\n" }; try { die "this" } catch { print "catched\n" } finally { print "done\n" } '
  this
  catched
  done

constant subroutines

prototype mismatch

  $ perl -e ' sub X () { 123 } print X, "\n"; eval " sub X { 456 } "; '
  123
  Prototype mismatch: sub main::X () vs none at (eval 1) line 1.
  Constant subroutine X redefined at (eval 1) line 1.

reference to scalar doesn't work

  $ node perlito5.js -Isrc5/lib -I.  -e ' use Data::Dumper; $v = [20, \$v ]; print Dumper ($v) '
  $VAR1 = [
          20,
          \undef,
      ];

assign old-self to my / local
```
  local $Some_Global = $Some_Global;
```
missing some types of subroutine signatures
AUTOLOAD() called from UNIVERSAL autovivifies packages

add tests

delete() in the middle of an array turns exists() off:

  $ perl -e ' @a = (3..7); delete $a[2]; print "exists ", (exists $a[$_] ? 1 : 0), "\n" for 0 .. $#a '
  exists 1
  exists 1
  exists 0
  exists 1
  exists 1

delete() in src5/lib/Perlito5/Grammar/String.pm doesn't seem to work:

  delete($quote_flags->{$flag_to_reset});
  delete($quote_flags->{last_flag});

~~ operator not implemented; See also when implementation
given statement not implemented
when should use a break exception inside given, and a next exception inside for.
default statement not implemented
javascript errors don't show in the global error handler when running in node.js
"autoload" the compiler if eval-string or require() are used (eval-string needs the compiler at run-time)

#23
symbol variables like $] ${"main::\$"} $#_
check that @_, $_, $a, $b and other special variables are in the right context (lexical, global, package global)
add alternate mro's
cache the mro
add regex compiler
support all perl5 regex syntax
@v = /x/g
regex variables localization in blocks $ perl -e ' "a" =~ /(.)/; print $1; { "b" =~ /(.)/; print $1; } print $1, "\n"; ' aba $ perl -e ' "a" =~ /(.)/; print $1; { "b" =~ //; print $1; } print $1, "\n"; ' abb $ perl -e ' "a" =~ /(.)/; print $1; { "b" =~ /x/; print $1; } print $1, "\n"; ' aaa

some qr() and quotemeta() details

  $ perl -e ' my $x = qr/ \A x /x; my $y = qr/$x y \Q[z]/; use Data::Dumper; print Dumper $x; print Dumper $y; '
  $VAR1 = qr/(?x-ism: \A x )/;
  $VAR1 = qr/(?-xism:(?x-ism: \A x ) y \[z\])/;

  $ perl -e ' print " a b \Q [ a \nn"; '
   a b \ \[\ a\ \
  n

  $ perl -e ' print "x\Q[\Qx]\Ex\n" '
  x\[x\\\]x\          # '\' is quoted, but 'Q' disappears

qr() returns a Regexp object

  {
      package Regexp;
      sub x { 123 }
  }
  $a = qr//;
  print $a->x, "\n";  # 123

lvalue ternary: ($a_or_b ? $a : $b) = $c;
lvalue substr()
4-arguments substr()
lvalue pos($str)
pos($str)
lvalue chomp(), chop()
lvalue subroutine

bug: variable aliases create copies instead

  for (@x) { $_++ }   # doesn't change @x

generate more compact code; maybe use more subroutines instead of inlining;

autovivification is probably the most verbose part of the code.

Use less throw - it is not (yet?) optimized by V8
in the browser: implement use with XMLHttpRequest (what are the security implications?)

aliasing between lexicals and globals

  $ perl -e 'use strict; my $x = 3; *main::z = \$x; print $main::z; '
  3

finish overload implementation

See: p5str
pack(), unpack()
flip-flop operator

if either operand to scalar '..' is a constant the value is implicitly compared to the input line number ($.)

caller() in nodejs and Chrome:

See: https://github.com/stacktracejs

$ nodejs perlito5.js -Isrc5/lib -I. -e ' sub x { print JS::inline("new Error().stack") }; sub yy { x() }; my $f = sub { yy() }; $f->() '

"Error
  at tmp104 [as x] (eval at <anonymous> (/perlito5.js:31586:57), <anonymous>:10:63)
  at tmp105 [as yy] (eval at <anonymous> (/perlito5.js:31586:57), <anonymous>:18:26)
  at tmp106 (eval at <anonymous> (/perlito5.js:31586:57), <anonymous>:27:28)
  at eval (eval at <anonymous> (/perlito5.js:31586:57), <anonymous>:32:7)
  ..."

die() details

If the output is empty and $@ already contains a value (typically
from a previous eval) that value is reused after appending
"\t...propagated". This is useful for propagating exceptions:

    eval { ... };
    die unless $@ =~ /Expected exception/;

If the output is empty and $@ contains an object reference that
has a "PROPAGATE" method, that method will be called with
additional file and line number parameters. The return value
replaces the value in $@; i.e., as if "$@ = eval {
$@->PROPAGATE(__FILE__, __LINE__) };" were called.

my sub x {...}

Implemented but missing more tests

add tests: my variables - this doesn't work as expected: my $v = $v

add tests using closures, to check that the redeclared variable is a different variable

  $ perl   -e '  my $x = 10; print "$x\n"; my $x; print "$x\n"; '
  10
  [space]
  $ nodejs perlito5.js -Isrc5/lib  -e '  my $x = 10; print "$x\n"; my $x; print "$x\n"; '
  10
  10

/e modifier
lvalue $#a

local

add tests: exiting a block with 'last' doesn't retrieve previous 'local' values:

  $ nodejs perlito5.js -Isrc5/lib -I. -It  -e ' $_ = "abc"; /(b)/; print "$1\n"; { print "$1\n"; /(c)/; print "$1\n"; last; } print "$1\n"; '
  b
  b
  c
  c

& prototype

add tests; see Try::Tiny
add symbol tables for scalar, array and hash

references to typeglobs:

  $ perl -e ' print ref(\*main) '
  GLOB

prototype() can be set by aliasing:

*x = sub ($$) { 123 }; *y = *x; print prototype(\&y) # $$
or has SCALAR context (Abigail++):

See: t5/01-perlito/23-eval.t

'next', 'last' in expression

(*{"${callpkg}::$sym"} = \&{"${pkg}::$sym"}, next)
... ) and last

check that \(@a) and \@a have different meanings
'x' in list context

@{$cache}{@$ok} = (1) x @$ok;
while () {}

this is implemented - it now needs some tests:

http://blogs.perl.org/users/peter_martini/2014/05/spelunking-why-while-is-my-new-favorite-perl-ism.html
```
while () {}     # infinite loop - while(1)
while (()) {}   # no loop
```

pass @_ to &sub

$ node perlito5.js -I./src5/lib -Cjs -e ' @_ = (1,2);  &foo; '
# call foo(@_)

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README-perlito5-JavaScript.md

README-perlito5-JavaScript.md

Perlito5-in-JavaScript

Command line

Perlito5-in-JavaScript - what works

Perlito5-in-JavaScript differences from "perl"

Calling Perl subroutines from JavaScript

Calling JavaScript methods from Perl

Internals

Perlito5 JavaScript Data model Overview

JavaScript resources

Regex

Cell-based aliasing (TODO)

Tail call (TODO)

"js3" virtual machine

Perlito5 JavaScript backend TODO list

Features

Implemented but missing more tests

Files

README-perlito5-JavaScript.md

Latest commit

History

README-perlito5-JavaScript.md

File metadata and controls

Perlito5-in-JavaScript

Command line

Perlito5-in-JavaScript - what works

Perlito5-in-JavaScript differences from "perl"

Calling Perl subroutines from JavaScript

Calling JavaScript methods from Perl

Internals

Perlito5 JavaScript Data model Overview

JavaScript resources

Regex

Cell-based aliasing (TODO)

Tail call (TODO)

"js3" virtual machine

Perlito5 JavaScript backend TODO list

Features

Implemented but missing more tests