[PD] selecting triggers once with env~?

[Roman Haefeli via Pd-list]

On Mon, 2014-06-09 at 19:53 -0700, Ronni Montoya via Pd-list wrote:
> Hi, im tracking the amplitude of my signal with ~env and i need to
> send one trigger when my ~env gives 0 , the problem is that if i do:
> 
> ~env
>    |
> select 0
> 
> 
> It send a lot of triggers when my ~env is in 0 and i need to send just
> one trigger.
> 
> any idea how can i send only one trigger ?

There is [change] which only lets changing values pass. Something like
this should work:

[env~ ]
|
[change]
|
[select 0]

Roman