Unexpected Random behaviour in Recursive Function.

RE: Unexpected Random behaviour in Recursive Function.

jonathanb0001 — Tue, 29 Jan 2019 12:55:37 GMT

Wow been a while since this thread was active. Thanks for the response that's a really interesting approach that I'd never considered.

I'm a little concerned about using an expression like that due to the nature of the random function being applied multiple times.
Indexing a single value against a list guarentees that a single value will be selected however I don't see how your rule can ensure that one and only one value will be selected for each time the rule runs over the list.
That just sets off all sorts of alarm bells in my head.

Didn't know the Navy was looking for me. Jokes on them I don't own a boat so they'll be searching for a long time :P

RE: Unexpected Random behaviour in Recursive Function.

chrisc651 — Tue, 29 Jan 2019 11:39:06 GMT

You could also use reduce which is recursive, to remove a number of entries from the whole list, and then use difference to get the ones which have been removed. In this case the array of integers passed to reduce is only used to control the number of times it is called. Have the Navy given you a call yet ;)

difference(
  ri!inputArray,
  reduce(
    rule!removeRandArrayEntry,
    ri!inputArray,
    enumerate(
      ri!numTimes
    )
  )
)

RE: Unexpected Random behaviour in Recursive Function.

jonathanb0001 — Tue, 08 May 2018 15:53:48 GMT

It's now working however I can't find a satisfying reason why.
I added a length parameter which tracked the range for the random number and it was constantly 1.
I expanded the lists of dictionaries for boardIds by adding a forEach statement which just returned each item. Now it works... My best guess is that Appian was struggling with list/dictionaries (Maybe it was seeing a list of list of dictionaries? However in that case I'd have expected it to append all of them at once.). And that the for each restructured it into something it found easier to handle.
Yeah, It doesn't really make sense to me.

RE: Unexpected Random behaviour in Recursive Function.

Josh — Fri, 04 May 2018 16:58:51 GMT

I think the root of this issue lies in your implementation somewhere. I whipped up a simple recursive rule that uses rand() and returns ri!numTimes random numbers from 1 - ri!range. Running this rule results in a list of different random numbers each time. This seems to rule out any issues with rand() and recursion.

if(
  ri!numTimes = 0,
  null,
  append(
    roundup(rand() * ri!range),
    rule!this_rule(
      numTimes: ri!numTimes - 1,
      range: ri!range
    )
  )
)

RE: Unexpected Random behaviour in Recursive Function.

jonathanb0001 — Fri, 04 May 2018 15:07:05 GMT

Afraid not. That doesn't explain the problem with the behaviour as if it wasn't being reevaluated it would just take the same index value each time rather than taking a random one and then always taking the 1st.

However to be thorough I did try this. Even after both loads are changed to with it doesn't change how the process works.

I think the problem with your solution is that despite appearances each local!index is created in its own separate Load() and as theres no user interaction it actually never receives a signal telling it to refresh the value anyway.

RE: Unexpected Random behaviour in Recursive Function.

Carlos Santander — Fri, 04 May 2018 15:00:42 GMT

Your local!index variable doesn't get updated because it's in a load(). Change that to with() and it should work.