Implementing a Queue

#1

I’m slowly working on moving some of my old SmartApps to pistons. One of them used groovy’s Queue class.

Is there a way to use this class (or something equivalent) within a piston?

(creating a queue) Append to a list of strings while pulling the first item in the list
#2

i have kind of like a queue implemented in one of my pistons, but only if you squint just the right way. :slight_smile:

theres no way to use the queue class in wC that i know of. but you could use a list[…] variable with pointers to implement a queue within wC.

#3

heres the piston that does it. remember i said you have to squint. :slight_smile: but the basic principle of a queue implementation is the same as what is done here with colorsToShow and colorIndex.

#4

Another way to manage a queue with a single variable is to leverage a comma-separated string variable which will act like an array when provided to some of the array functions. This may be a useful solution if you have to manage several queues in a single piston and don’t want to track indexes for all of them.

Here is an example piston that shows expressions that could be used to manage a comma-separated string queue. Note that arrayItem() and count() interpret a comma-separated string as a list.

queue
queue.png1178×783 145 KB

The following test runs through a few basic operations:

queue_test
queue_test.png1178×766 173 KB

for which the Queue piston logs:

26 PM
Screen Shot 2017-10-13 at 12.21.26 PM.png585×814 88.8 KB

Don’t get too excited about this “Queue” piston though, you probably can’t use it how you would want (execute from other pistons and get the result). The real-life scenario would involve using the expressions shown to interact with the queue in a single piston.

#5

why not use a list[…] variable like already shown in the example posted above yours? :slight_smile:

#6

Because it’s quite a bit more work and you have to keep track of a few indexes to know which part of the queue is still alive, I suppose.

#7

that’s easily done with 3 indexes and a cleaner solution than trying to use string variable for it.