>>>>> "ML" == Markus Laker <u20090103.20.mla...@spamgourmet.com> writes:
ML> Adding a single backslash before `eval' pushes an anonymous array on to
ML> @b, as you envisage wanting to do:
ML> # Imagine that @a.perl has produced this:
ML> my $p = "('blue', 'light', 'hazard')";
ML> my @b;
ML> @b.push(\eval $p);
but that is manual code. what about a larger tree?
>> a more useful example would be serializing data trees. if you dump @b
>> with .perl do you want the current dumper output of a anon array or your
>> list of values? when serializing a tree, you must get the ref version so
>> that is the common and default usage. your version isn't DWIMmy there at
>> all.
ML> I think Perl 6's automatic reference-taking (though we don't call them
ML> references any more) solves that problem for us.
ML> If you say
ML> my @c = eval '(1, 2, 3)';
ML> then @c has three elements. If you say
ML> my $c = eval '(1, 2, 3)';
ML> then Perl constructs (if I've got the Perl 6 lingo right) an Array object
ML> and stores it in $c. So the round brackets DTRT whether you're storing
ML> into an array like @c or into a scalar like $c.
that fails with nested arrays. we don't want them to flatten.
my $c = eval '(1, (4, 5), 3)';
will that work as you envision? in perl5 with [] it works fine. i know
there are contexts that flatten and others that don't. but a larger tree
with assignments like that are harder to read IMO as lists inside lists
are not nesting but flattening in p5 all the time.
ML> We serialised an array of three elements; we got back an array containing
ML> just one. Round brackets would have solved that. (Actually, we don't
ML> need any brackets at all, because Perl 6's list constructor is a comma,
ML> not a set of brackets. But round brackets would be no-ops, and they
ML> arguably make the output more human-readable.)
try that again with my example above. in p5 the structure would be this:
my $c = [1, [4, 5], 3] ;
how should .perl serialize that so that eval will give back the same
structure? unless () are nesting and not flattening then you can't do it
without a \() which is longer (and uglier IMO than []).
uri
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