Hi,
quoting http://dev.perl.org/perl6/synopsis/S06.html:
> Pairs can be used as lvalues. The value of the pair is the
> recipient of the assignment:
>
> (key => $var) = "value";
>
> When binding pairs, names can be used to "match up" lvalues
> and rvalues:
>
> (who => $name, why => $reason) := (why => $because, who => "me");
that's really convenient, but what will the following code do?
my $x = (a => 42); # $x is a Pair.
$x = 13; # Is $x now the Pair (a => 13) or
# the Int 13?
When executing the second line, $x is a Pair. And it is used as a
lvalue. So, according to S06, the assignment will only change the
value of the Pair, not the Pair itself.
But I doubt this is what most programmers will expect -- example:
sub foo (Any $x) {
$x = 13; # Won't always make $x an Int.
...;
}
my $pair = (a => 42);
foo($pair);
So, does this Pairs-as-lvalue rule only affect "real syntax-Pairs"?
If not, what would the sub unpairify in the following code have to
look like?
my $x = (a => 42);
unpairify($x, 13);
# $x is now the Int 13.
sub unpairify (Any $x is rw, Int $num) {
...; # fill in please
}
--Ingo
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generation on a dual AMD- |
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