[PD] trouble with data structures

[Frank Barknecht]

Hallo,
Julian Peterson hat gesagt: // Julian Peterson wrote:

> I'm writing my first piece that will take advantage of data structures
> in PD, and I've stumbled upon an error that I do not understand.
> 
> I have two structures drawn in the same subpatch.  One is a sequence of
> notes, the other is a playhead.  The sequencer was working fine until I
> added the playhead.  Now whenever I try to get data from the sequencer
> (getsize, get) I receive the following error:
> 
> error: getsize pd-instr1: got wrong template (pd-playhead)
> 
> My patch is attached below.  Is it not possible (or not advisable) for
> two structures to draw to the same subpatch?

You forgot to attach the patch, but I guess what's happening is some
error in traversing the data structures in the patch. If you mix
several types in a subpatch - which is perfectly possible - you need
to be aware, that on traversal of this subpatch you will hit pointers
of different type. So assuming you have a [struct a float x] and [struct
b float x] in your patch, then if you do this:

  [traverse pd-data, next(
  |
  [pointer]

what comes out of [pointer] may be a pointer to "a" or a pointer to
"b". So if you try to [get] at the data using this:

  [get a x]

you will get an error everytime, the incoming pointer is of type "b",
because then you'd need to use [get b x] instead. 

A way out can be this construct: 

  [traverse pd-data, next(
  |
  [pointer a b]
  |     |     |
  |     |     ... do something else here 
  |     |
  |     [get b x]
  |
  [get a x]| 

Ciao
-- 
 Frank Barknecht                 _ ______footils.org_ __goto10.org__