# [PD] The Issue with 2 or more inlets

Frank Barknecht fbar at footils.org
Tue Aug 16 17:28:19 CEST 2005

```Hallo,
Sebastian Schwerdhoefer hat gesagt: // Sebastian Schwerdhoefer wrote:

> I'm about to learn puredata, but I didn't reach very far. I understood
> the issue with 2 or more inlets, and read, that a trigger could help
> - but never found an example for that.
>
> I'm not shure if i really understood that trigger thing, so can anyone
> look at "my" example?

The left example also "works", it just works differently than the
right one.

The long explanation (print this)
--------------------------------

The right part with the trigger will always output the sum of both
numbers, whereas the left part realizes a "muted" addition. Here you
can set the number to add without generating any output, until a
number is sent to the leftmost inlet. That's why the leftmost inlet
also is called the "hot" inlet here, the right inlets are "cold"
inlets.

If you think about it: The trigger object triggers its *outlets*
in exactly the *opposite* order. That is, first the rightmost outlet
fires, then the next one until at last the leftmost outlet fires.

This makes sure, that if you directly connect outlets to inlets
without making crossed connections, the cold *inlet* of any
*following* objects gets its data as the *last* one. So all setup and
stuff done through the other inlets can happen an be finished first.

A good example is squaring a number:

[3(
|
[t f f]   == [trigger float float]
|     |
[*    ]
|
9

Here the right trigger outlet will fire first, so the internal
multiplicator of [* ] will set to be "3". No output is generated.

Then the left outlet of trigger fires and sends another "3", which
will get multiplied with the "3" stored previously. *Now* the [*] will
send "9" along as now its "hot" inlet was triggered.

If you send a "4" into the trigger, it will correctly output "16" as
the previously stored "3" will be overwritten with a new "4" at the
right moment.

If you consider the other possible connection, you cannot be sure of
the result unless you now the history of the patch:

[3(
|
[t f f]
\ /
x
/ \
[*  ]
|
?

Will there be a 9 here? Or a 3? Or a 0? And when?

It also is instructive to look at one of the rare objects, where the
hot inlet is left: [timer].

A typical [timer] idiom is this:

[t b b]
|    |
[timer]
|

which will give the time differenc between two incoming bangs. See the
help patch for timer to learn why.

Ciao
--
Frank Barknecht                               _ ______footils.org__

_ __latest track: "plak" @ http://footils.org/cms/show/44

```