TODO-perlito5

TODO list for Perlito5


* perlito5 command-line


* libraries

-- these should probably go into namespace Perlito5X::*

-- Test (implemented as Perlito5::Test)

-- Data::Dumper (implemented as Perlito5::Dumper)

-- create perlito5-specific libs for:
    feature.pm
    Config.pm
    overload.pm
    bytes.pm
    integer.pm
    constant.pm
    lib.pm
    Carp.pm
    vars.pm
    Tie::Array
    Tie::Hash
    Tie::Scalar

    alternately, check $^H for strictness - such that perl's own strict.pm just works
    and ${^WARNING_BITS} for warnings


* Parser

-- dot-decimal strings
    5.4.66.77
    v5.4.66.77

    $ perl -e ' my $v =  5.4.66.77 ; print $v, "\n"; require $v '
    BM

-- "'" meaning "::"
    $'m  # $::m
    $m'  # String found where operator expected

    package X'Y  # X::Y
    package X'   # Invalid version format (non-numeric data)

-- attributes
    http://perldoc.perl.org/attributes.html
    missing MODIFY_CODE_ATTRIBUTES handlers

-- create __DATA__
    %Perlito5::DATA_SECTION contains the __DATA__ for each package 

-- compile-time eval() is not bound to the "program" environment, but to the "compiler" environment instead
    see README-perlito5-js near "Compile-time / Run-time interleaving"

    my $v;
    BEGIN { $v = "123" }
    use Module $v;  # $v is not accessible at compile-time

-- parse the regexes
    create an AST for regexes

-- prototypes (signatures)
    http://perldoc.perl.org/perlsub.html#Prototypes

    check that undeclared barewords give the right error
    *foo = sub () { ... }   # does prototype work here?
    check signature in sort()
    fix the prototype for 'stat(*)' (see t/test.pl in the perl test suite)

-- "namespace" parsing
    tests: t5/01-perlito/26-syntax-namespace.t

    $ perl -e ' { package X; sub print { CORE::print(">$_[1]<\n") } } my $x = bless {}, "X"; print $x "xxx" '
    Not a GLOB reference at -e line 1.

    $ perl -e ' { package X; sub printx { CORE::print(">$_[1]<\n") } } my $x = bless {}, "X"; printx $x "xxx" '
    >xxx<

    $ perl -MO=Deparse -e ' print X:: "xxx" '
    print X 'xxx';

    $ perl -e ' use strict; my $x = X::; print $x '
    X

    $ perl -e ' use strict; my $x = X; print $x '
    Bareword "X" not allowed while "strict subs" in use 

    $ perl perlito5.pl -MO=Deparse -e ' ::X::x::y '
    join("", ::{'main::X::'} x main::y);

    $ perl -MO=Deparse -e ' ::X '
    '???';

    $ perl -MO=Deparse -e ' sub X {} ::X '
    sub X { }
    X;

    $ perl -e ' $::X::::X = 3; print $main::X::::X '        # 3
    $ perl -e ' $::X::::X = 3; print $main::main::X::::X '  # 3
    $ perl -e ' $::X::::X = 3; print $main::X::main::X '    # empty
    $ perl -e ' $::X::::X = 3; print $main::X::X '          # empty
    $ perl -e ' $::X::::X = 3; print $::::X::::X '          # empty

-- CORE:: namespace can be used with operators:

    $ perl -MO=Deparse -e ' $x CORE::and $v '
    $v if $x;

    $ perl -MO=Deparse -e ' @v = CORE::qw/ a b c / '
    @v = ('a', 'b', 'c');

    $ perl -MO=Deparse -e ' $x CORE::+ $v '
    CORE:: is not a keyword


-- strict and warnings: create options like 'subs', 'refs'

-- clean up:
    the several "end_tables" in Expression.pm are duplicating the function of 
    $Precedence in Precedence.pm - Expression.pm should use $Precedence directly.

-- things that work in perlito5, but which are errors in 'perl'

    $ perl -e ' my @things= map {  no warnings; 123 } @list; '
    "no" not allowed in expression

    quotes vs. hash lookups:
    
        $ perl -e '  q}} '
        # ok
    
        $ perl -e ' $x{ q}} } '
        Unmatched right curly bracket at -e line 1, at end of line
    
        $ perl -e ' $x{ q]] } '
        # ok
    
    string interpolation with nested quotes of the same type:
    
        $ perl -e ' " $x{"x"} " '
        String found where operator expected at -e line 1, near "x"} ""


* Add tests for fixed bugs:

    ---
    variable declarations in expressions

    our $Verbose ||= 0;
    our (%Cache);
    my $args = @_ or @_ = @$exports;


    ---
    add additional variants of "for"

    # "our" with localization
    $ perl -e ' use strict; our $x = 123; for our $x (1,2,3) { 2 } print "$x\n" '
    123

    # variable in scope with localization
    $ perl -e ' use strict; my $x = 123; for $x (1,2,3) { 2 } print "$x\n" '123
    123


    ---
    add "print", "printf", "say" special parsing - note this is related to indirect object notation

    indirect object notation
    http://lwn.net/Articles/451486/
    http://www.modernperlbooks.com/mt/2009/08/the-problems-with-indirect-object-notation.html
    http://shadow.cat/blog/matt-s-trout/indirect-but-still-fatal/
    http://perlbuzz.com/mechanix/2008/02/the-perils-of-perl-5s-indirect.html

    method Module $param;
    new Class( arg => $value );
    new Class::($args);
    say $config->{output} "This is a diagnostic message!";  # indirect call
    say {$config->{output}} "This is a diagnostic message!"; # say to filehandle

    use Class;
    sub Class {
    warn 'Called Class sub not Class package';
    'Class'
    }
    my $q = Class->new; # calls the Class sub above
    my $s = new Class; # throws a 'Bareword found where operator expected' error
    my $t = Class::->new # this works
    my $u = new Class::; # this also works (even with sub main in the current package)

    sbertrang++ noted this is also valid:
    print( STDERR "123" )


    ---
    add tests for signatures: "empty" _ $ ;$

    ---
    add test for "sub _" should be in package "main"
    $ perl -MO=Deparse -e ' package X; sub _ { 123 } '
    package X;
    sub main::_ {
        123;
    }

    ---
    add test for defined-or vs. m//  (2012/9/25 Конрад Боровски <notifications@github.com>)
    Note: fixed; see test t5/01-perlito/25-syntax-defined-or.t

    $ perl perlito5.pl -Isrc5/lib -Cast-perl5 -e ' shift // 2 '
    Number or Bareword found where operator expected

    $ perl perlito5.pl -Isrc5/lib -Cast-perl5 -e ' shift / 2 '
    Can't find string terminator '/' anywhere before EOF

    ---
    add test for filetest operators special case:
    ' -f($file).".bak" ' should be equivalent to -f "$file.bak"
    parses as -(f($file)).".bak" 
    but: ' -f ($file).".bak" '
    parses correctly
    This seems to be because there is a rule that \w followed by '(' is a function call;
    this needs more testing: ' ... and(2) '
    Test: redefine 'and', 'not' and check what works.

    '  $s111++ + $s222 '
    parses as  (+$s222)++

    '  $step++ < $steps '
    Can't find string terminator '>' anywhere before EOF



* Perl5 backend

-- "given" statement not implemented
-- "default" statement not implemented

-- check that \(@a) and \@a have different meanings

-- ${^NAME} needs curly-escaping

- fix regex delimiters, or escape the regexes 

-- continue block in block: ' { print 1 } continue { print 2 } '

-- emitter bug: significant parenthesis: 
    t5/01-perlito/12-context.t fails because:
    " return (4, 5) " instead of " return 4, 5 "

-- bug: ' $$x [$y] '
    emits as ${$x}->[$y];


* Javascript backend

-- autovivification of fully-qualified array and hash globals
    $#{"Exporter::Cache"};

    ${"Exporter::Cache"}[2] = 3;

    See: p5scalar_deref() / p5scalar_deref_set() in Perlito5/Javascript2/Runtime.pm

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

-- dot-decimal strings / v-strings
    $ perl -e ' my $v =  5.4.66.77 ; print $v, "\n"; require $v '
    BM

-- variable declarations inside condition
    if ((my $color = <STDIN>) =~ /red/i) {
        $value = 0xff0000;
    }
    elsif ($color =~ /green/i) {
        $value = 0x00ff00;
    }
    else { ... }

    After the else, the $color variable is no longer in scope.

-- do {} while / do {} until
    execute the loop once, before checking the condition

-- 'require v5.006;'
    # Can't locate v5.006 in @INC

-- expressions in 'local'
    local $SIG{__WARN__};

-- assign old-self to my / local
    local $Some_Global = $Some_Global;

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

-- 'x' in list context
    @{$cache}{@$ok} = (1) x @$ok;

-- '&' prototype
    add tests; see Try::Tiny

-- AUTOLOAD() called from UNIVERSAL autovivifies packages
    add tests

-- prototype() can be set by aliasing:
    *x = sub ($$) { 123 }; *y = *x;  print prototype(\&y)   # $$

-- check that \(@a) and \@a have different meanings

-- 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

-- "or" has SCALAR context (Abigail++):
    See: t5/01-perlito/23-eval.t

-- "~~" 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

-- bug: some declarations are not "seen":
   for ( my $i = 0; $i < 10 ; $i++ ) { print "$i\n" }   # compiles to global $i

-- bug: don't emit throw() in term position; javascript requires a function() wrapper because throw() is a statement

-- javascript errors don't show in the global error handler when running in node.js

-- "autoload" the compiler if eval-string is used (eval-string needs the compiler at run-time)

-- 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
-- /e modifier
-- /x modifier
-- support all perl5 regex syntax
-- @v = /x/g

-- bug: variable redeclaration does not work
-- javascript "var" erases the outer value within the whole current lexical scope
-- bug: "my" variables - this doesn't work as expected: my $v = $v
   possible fix: rename variables

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

-- missing some types of subroutine signatures

-- bug: variable aliases create copies instead

-- generate more compact code; maybe use more subroutines instead of inlining;
   autovivification is probably the most verbose part of the code.

-- in the browser: implement "use" with XMLHttpRequest (what are the security implications?)

-- add symbol tables for scalar, array and hash
-- references to typeglobs:
    $ perl -e ' print ref(\*main) '
    GLOB
-- aliasing between lexicals and globals
    $ perl -e 'use strict; my $x = 3; *main::z = \$x; print $main::z; '
    3

-- string increment and string ranges
    See: p5str_inc()

-- finish "overload" implementation

-- pack(), unpack()
-- y()()

-- BEGIN{} should execute in the environment of the program under compilation
-- BEGIN/END that are defined inside blocks/closures need to run inside some pseudo-environment
    even if the closure was never created or used in the first place

-- bug - method call context is disabled, because it breaks bootstrap.
    in Runtime.pm:
    function p5call(invocant, method, list, p5want) {
        list.unshift(invocant);
        p5want = 0;  // TODO BUG - workaround for broken bootstrap

-- bug https://github.com/fglock/Perlito/issues/10
    "Perlito 5 JS has syntax errors"

    Tried
    
    YUI Compressor online
    and
    Google Closure Compiler
    http://closure-compiler.appspot.com/home
    
    Both failed with syntax errors.

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

-- unary minus on strings.

    my $_ = "a"
    print -$_
    # -a

    my $foo = '-bar';
    print $foo;
    print -$foo;
    # -bar+bar


* Nice to Have

-- debugging symbols
-- line numbers in error messages

-- caller()
-- "when"

-- run more of the "perl" test suite

-- proper "use strict" and "use warnings"
-- use the same error messages and warnings as 'perl'
-- no warnings 'redefine';

-- __LINE__, __FILE__

-- INIT{}, END{}
   look at the implementation in perlito6-in-Go

-- source code - remove Perl 6 code such as "token"
   (fixed: This is only loaded if the grammar compiler is needed)

-- *{ $name }{CODE}->();

-- local(*{$caller."::a"}) = \my $a;
-- *{$pkg . "::foo"} = \&bar;


* Oddities

-- from moritz, Schwern and others at
    http://stackoverflow.com/questions/161872/hidden-features-of-perl

    - you can give subs numeric names if you use symbolic references

    $ perl -lwe '*4 = sub { print "yes" }; 4->()'
    yes

    - you can use letters as delimiters

    $ perl -Mstrict  -wle 'print q bJet another perl hacker.b'
    Jet another perl hacker.
    
    Likewise you can write regular expressions:
    
    m xabcx
    # same as m/abc/

    The "desperation mode" of Perl's loop control constructs which causes them to look up the stack to find a matching label allows some curious behaviors which Test::More takes advantage of, for better or worse.
    
    SKIP: {
        skip() if $something;
    
        print "Never printed";
    }
    
    sub skip {
        no warnings "exiting";
        last SKIP;
    }


* Deprecate

-- remove unused features from src5/lib/Perlito5/Grammar/Regex.pm

-- Interpreter backend
   this is not being maintained; the code is still in src5/lib/Perlito5/Eval.pm just in case

-- Perl6 backend (started)
   this is not being maintained; not sure if compiling to Perl6 is the best way
   maybe compiling directly to Parrot/dotnet/Haskell gives better results