[PD] How to implement an @ argument in an external object?

[Claude Heiland-Allen]

Hi Alexandros

You can compare symbols for string equality by pointer equality (because 
symbols are interned in a table and never released - fast equality check 
is the whole point of symbols in Pd).

Something like this (untested):

static t_symbol *s_at_sync = 0;
extern void foo_setup(void)
{
   s_at_sync = gensym("@sync");
   ...
}

void *foo_new(int argc, t_atom *argv)
{
   if (atom_getsym(argv[3]) == s_at_sync)
   {
      sync();
   }
   ...
}

Or you can get the pointer to the symbol's string from the symbol 
struct, see m_pd.h for details.  You must not modify the string, but you 
could access it to see if it starts with '@' for example.


Claude

On 02/08/18 21:02, Alexandros wrote:
>
> Coming back to this thread after some time.
>
> I'm trying to check whether a given argument to an external I'm 
> writing starts with "@" or if it is actually "@sync", but can't seem 
> to make it work. Can't really understand how t_symbol works. I'm 
> iterating though the arguments with int argc and t_atom *argv and if 
> there are the right number of arguments, I'm retrieving the argument 
> that's supposed to be "@sync" with atom_gensym(argv);
>
> I don't know how to compare that to a hard-coded string, like "@", or 
> "@sync". I tried comparing straight to these strings, tried strcmp(), 
> but I don't know how to do this, and couldn't find examples online.
>
> Any hints?
>
>
> On 26/02/2018 07:36 μμ, IOhannes m zmölnig wrote:
>> On 02/26/2018 08:09 PM, Alexandros wrote:
>>> Being informed about the mailing list archive correct link, I searched
>>> for messages about this but didn't find something (it's possible I've
>>> missed something though).
>>>
>>> I'm writing an external and I want to use an @ argument (for example
>>> "@sync hard"). How does one implement this in C code?
>>>
>> either use flext (but then you write C++) and it comes for free.
>>
>> or simply iterate over the arguments, looking for symbols starting with
>> "@" (or simply search for symbols that are "@sync"), then check whether
>> there's another argument after that and see which value it has.
>>
>> fgdamrs
>> IOhannes
>>
>>
>>
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>
>
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