On 07/03/2015 07:20 PM, Tom Browder wrote:
> On Fri, Jul 3, 2015 at 10:26 AM, Tom Browder <[email protected]> wrote:
>> While experimenting I've found the first two methods of passing a hash
>> to a subroutine work:
>>
>> # method 1
>> my %hash1;
>> foo1(%hash1);
>> say %hash1.perl;
>> sub foo1(%hash) {
>> %hash{1} = 0;
>> }
> Another question on method 1 above, please:
>
> What is the proper type to use for the %hash for a more complete
> signature in function foo1? I've tried various types such
> Associative, Hash, and Any and gotten an exception.
>
> Thanks,
>
> -Tom
When you define a parameter with a % sigil or a @ sigil (or even a &
sigil) in your signature, you'll get the right kind of type restriction
"for free".
Try this:
> perl6 -e 'sub foobar(%i) { }; foobar((1, 2, 3))'
> Type check failed in binding %i; expected 'Associative' but got 'Parcel'
If you declare an additional Type to be matched against, you
parameterize the Associative (or Positional in case of an @ sigil) type
you require to be passed.
Something that very often surprises newcomers is that this works:
> sub takes_int_array(Int @bar) { say @bar }
> my Int @foo = 1, 2, 3;
> takes_int_array(@foo)
but this does not
> sub takes_int_array(Int @bar) { say @bar }
> takes_int_array([1, 2, 3])
because the type match is against the defined type. We do not
automatically infer that [1, 2, 3] could be a Positional[Int].
Hope that helps and I've also successfully predicted your next stumbling
block for you :)
- Timo
