Hi

Hmm ... you are bringing some new aspects in, like mixing old and new syntax, instead of switching it globally for the whole file with a use feature right after use strict .

I didn't think to have a block scoped switching of syntax, don't think this would be wise.

(and I'm no expert of Perl6 variable syntax, I only know that plenty of stuff must change as a consequence)

Then it obvious now that @a and $a=\@a can't be automatically combined without braking some "traditions".

• Either $a has to be readonly, because the reference of @a is normally guaranteed to be immutable for it's lifespan.
• or @a should be an alias of @$a and always reflect the list form of wherever $a points.

(see also here )

I think the latter is what people rather accept.

Now if mixing with old code is the goal, I'd suggest a new declaration syntax for typed references by adding parens (additionally to untyped scalars)

my $arr[] = [42,43,44]; # "typed" array ref

#--- effects
print $arr[0];          # => 42         (same as $arr->[0])
print $arr;             # => ARRAY(0x8f4c214)
print "@arr";           # => "42 43 44" (same as "@$arr")
print "@arr[0,2]";      # => "41 43"    (slice)


#--- caught Errors (compile time):
my @arr;                ## @arr masks earlier declaration in same scop
+e
my $arr;                ## $arr masks earlier declaration in same scop
+e
my $arr{}               ## $arr{} masks earlier declaration in same sc
+ope
[download]

This "typing" references wouldn't not only facilitate syntax (by restricting the name space) but also add a lot of compile time checking.

for instance the following is only a run time error at the moment which could be avoided otherwise at compile time.¹

my $a_ref = [1,2,3];    # old style
$a_ref->{x};            ## Not a HASH reference (run time)
[download]

Furthermore did I follow Damian's naming convention here to mark a reference with a trailing _ref , to clearly indicate references to avoid typos, (albeit his convention doesn't distinguish types, that's why I personally prepend a_ to identifiers of arefs)

BUT if we had such typed references we could delegate this marking (which is a poor man's form of typing! ) to the syntax highlighting of the IDE after declaration in a scope and lazily avoid adding all those markers.²

Nota bene, the old syntax of my ($scalar, @array) wouldn't be effected and could be easily mixed

The my ($arr[], $hash{}, $code() ) syntax is of course debatable... am open for better ideas.

What do you think?

footnotes

¹) and compile time means almost immidiately for users of "flymake-mode" in emacs or komodo.

²) emacs already supports different styles ("cperl-...-faces") for arrays, hashes and barewords

UPDATE

the difference to the original suggestion is that it doesn't facilitate/change the use of the classical @a=(1,2,3) or $a=[1,2,3] but blends in with new syntax. (in other words easier for Perl cracks but less comfortable for beginners)

Since $scalars are all purpose variables it might be acceptable to still insist that references of untyped scalars are followed by a deref -> operator (?)

Cause if a $var could hold any reference, then the extra typing of -> could make this obvious like in $var->{x} vs $var->[1]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.