[PD] dealing with arguments and inlets

Hans-Christoph Steiner hans at eds.org
Sat Feb 4 02:32:55 CET 2006

On Jan 31, 2006, at 6:16 AM, Frank Barknecht wrote:

> Hallo,
> Hans-Christoph Steiner hat gesagt: // Hans-Christoph Steiner wrote:
>> I have written some classes for handling arguments when writing 
>> classes
>> in Pd.  They are [float_argument], [symbol_argument], and
>> [any_argument].  Currently, I am thinking in general,  inlets should 
>> be
>> matched to arguments and vice versa,
> "should match" would be oversimplyfiying, but having an extra inlet in
> the argument-patches never hurts.
>> so these objects all have a
>> "convenience" right inlet, to attach the [inlet] to so that the data
>> all comes from the [*_argument] object.
>> To use them, you add the argument you want it to handle like this:
>> [float_argument $1]
>> If you want a default value for when none is specified, you would do 
>> it
>> like this:
>> [float_argument $2 234]
>> [symbol_argument $3 default]
>> [any_argument $9 asdf]
>> [any_argument $5 444]
> I attached "list_argument" which does the same as "any_argument" but
> doesn't require any externals and is much simpler than [any_arg...].
> In fact, it's just [float_argument] where "float" is replaced by "list
> append".
> Note that I would much prefer, if [list_argument] would be renamed to
> be [any_argument] and replace it.
> Reason is: The name "list_argument" could lead to wrong expectations: 
> It doesn't
> handle variable length lists as arguments, because that is impossible
> without externals like dollarg. It just handles one-element lists
> which get auto-converted to their respective type: "symbol x" or
> "float x".
> Of course it won't work with Pd < 0.39.
> Regarding symbol_- and float_argument: These could be implemented as:
>   [list_argument $1 $2] or [any_argument]
>   |
>   [route symbol] or [route float]
>   |
>   [outlet]
> to share more code. Because Pd autoconverts one-element lists, there
> will always be a proper selector to make [route] do The Right Thing.

I found one key difference between [any_argument] and [list_argument].  
[any_argument] outputs a non-symbol, [list_argument] outputs a symbol.  
So that means that if you want to handle messages like [word( with 
[list_argument], there will have to be this after it:

[route symbol]
[route word]

Personally, I think its better having the argument not be a symbol 
since its very likely that [route] will be involved soon after.  Also, 
for [list_argument], you'll need some extra logic on the convenience 
inlet to make sure that the output on the [outlet] is always 
consistent.  I attached a version of [list_argument] with this extra 
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[route float]
\         [symbol]
  \        /
   \     /
    \  /

This gets into another definition question.  What is the type in this  
message: [word(  Its not a "not-list list" since its not a list of any  
kind.  Pd itself doesn't call one element messages a "list".  And a  
"non-list element" would also include this: [5(.  So I guess its an  
"undefined element" to match "undefined lists".

So we have:
undefined element
undefined list

I guess we should just coin words for these, like undelement and  
undlist ;)  Let's check the thesaurus for list: inventory; or element:  
item, unit.  Or how about this: "untyped list" and "untyped element".



            "The arc of history bends towards justice."
                                            - Dr. Martin Luther King, Jr.

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