[Bro-Dev] Use of 'any' type

[Jon Siwek]

In the master branch, there are also type checking/casting 'is' and
'as' operators [1] and type-based switch statement [2] that may be be
useful.

- Jon

[1] https://www.bro.org/sphinx-git/script-reference/operators.html
[2] https://www.bro.org/sphinx-git/script-reference/statements.html#keyword-switch

On Thu, Aug 16, 2018 at 4:24 PM Jim Mellander <jmellander at lbl.gov> wrote:
>
> Thanks, Johanna - I think type_name() may suffice for the purposes I am envisioning.
>
> On Thu, Aug 16, 2018 at 1:57 PM, Johanna Amann <johanna at icir.org> wrote:
>>
>> Hi Jim,
>>
>> On 16 Aug 2018, at 13:40, Jim Mellander wrote:
>>
>>> It would be most convenient if the 'any' type could defer type checking
>>> until runtime at the script level.
>>>
>>> For instance, if both A & B are defined as type 'any', a compile time error
>>>
>>> "illegal comparison (A < B)"
>>>
>>> occurs upon encountering a bro statement
>>>
>>> if (A < B) do_something();
>>>
>>> even if the actual values stored in A & B at runtime are integral types for
>>> which comparison makes sense.
>>
>>
>> I think this is a bit hard to do with how things are set up at the moment internally - and it also does make type-checking at startup less possible-helpful.
>>
>> However...
>>
>>>
>>> If the decision could be made at runtime (which could then potentially
>>> throw an error), a number of useful generic functions could be created at
>>> the script level, rather than creating yet-another-bif.  A useful
>>> yet-another-bif would be 'typeof' to allow varying code paths based on the
>>> type of value actually stored in 'any'.
>>
>>
>> This already exists and I think you can actually use it to write code like that; you just have to cast your any-type to the correct type first. The function you want is type_name; it is e.g. used in base/utils/json.bro.
>>
>> Johanna
>
>
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