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Postings from March 2016
One thing I'd like to add to subroutine signatures is optional types.
Perl already supports
my Foo $x;
which currently isn't made much use of in core, apart from with 'use fields',
which allows a lexical holding a hash ref to have compile-time and
run-time checks on allowed hash keys.
Adding this to signatures should be a no-brainer. I propose that the
existing signature syntax be extended so that every $/@/%var can be
prefixed with an optional type, with the same semantics as existing
my declarations, e.g.
sub f(Int $i, Foo::Bar $fb, $plain) { ...}
Which would be semantically equivalent to
sub f {
my Int $i = $_[0];
my Foo::Bar $fb = $_[1],
my $plain = $_[2];
# ... plus arity checks, default values etc....
...;
}
This would be still be a compile-time error:
sub f(Int $) {...}
since it's a placeholder and not a variable.
I'm not currently proposing any new semantics for such typed variables.
--
The Enterprise successfully ferries an alien VIP from one place to another
without serious incident.
-- Things That Never Happen in "Star Trek" #7
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