[PD] bang vs empty list

[Jonathan Wilkes]

>________________________________
> From: Ivica Bukvic <ico at vt.edu>
>To: Jonathan Wilkes <jancsika at yahoo.com> 
>Cc: pd-list <pd-list at iem.at> 
>Sent: Friday, March 1, 2013 7:55 AM
>Subject: Re: [PD] bang vs empty list
> 
>
>To add to this, I cannot think of a scenario where you would want to differentiate between bang versus symbol bang. Please feel free to convince me otherwise.

Just one example:

If you parse a Pd patch in Pd you'll want to handle everything as lists, because
the moment you shave off the list selector you're in danger of outputting bad
messages:

"#X text 10 10 INLET_0 bang float symbol"

|
[route #X]
|
[route text]
|
[route 10]
|
[route 10]
|
[route INLET_0]
|
[route bang]
|
[route float]  <-- oops, "float" got silently discarded above


Of course that's just a didactic example, because in real life you
would iterate over the message one atom at a time, and if "bang"
and "float" had been switched above you'd even get an explicit error
about "Bad arguments" (since float needs to be followed by a
float atom and not the symbol atom "bang").  Therefore you have
to use list objects to ensure you don't lose data or run into a badly
formed mesage, and when you split lists you end up with "symbol bang"
which [select] handles perfectly well.


The point is that select inspects the payload of the message and not the
selector.  Bang messages don't have a payload so you've now made a special
case where the selector is inspected only if the user types "bang" as an arg. The
[route] object already chooses bases on selector so I don't see a reason to change
the behavior for [select] in this way.


-Jonathan


>On Mar 1, 2013 7:50 AM, "Ivica Bukvic" <ico at vt.edu> wrote:
>
>Yes, but it also prevents profuse errors on the console regarding how select does not understand things which may happen in complex patches under certain circumstances, and which previously were not reported.
>>On Mar 1, 2013 3:29 AM, "Jonathan Wilkes" <jancsika at yahoo.com> wrote:
>>
>>----- Original Message -----
>>>
>>>> From: Ivica Ico Bukvic <ico at vt.edu>
>>>> To: pd-list at iem.at
>>>> Cc:
>>>> Sent: Thursday, February 28, 2013 7:15 PM
>>>> Subject: Re: [PD] bang vs empty list
>>>>
>>>> BTW, the only regression with this is that [select] object complains it does not
>>>> understand "bang."
>>>
>>>Pd's [select] only understands symbol and float messages.  If you make it
>>>accept bangs then you create an inconsistency where both
>>>"symbol bang" and "bang" are matched by [sel bang].
>>>
>>>-Jonathan
>>>
>>>> I've patched it so that when it receives a bang
>>>> it redirects it to sel1_symbol and sel2_symbol with a gensym("bang").
>>>> This also means that [sel b] would not work for bangs, but [sel bang] will. I
>>>> think that makes sense since someone might want to select letter "b."
>>>>
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>
>