Function

These functions existed? Never heard of them.

You can use this code instead. 

a!localVariables(
  local!data: a!forEach(
    items: ri!array,
    expression: { value: fv!item }
  ),
  todatasubset(
    local!data,
    a!pagingInfo(
      startIndex: 1,
      batchSize: - 1,
      sort: a!sortInfo(field: "value", ascending: or(ri!ascending))
    )
  ).data.value
)

Isolate this in an expression rule and use it anywhere in your app. 

yes but somehow I'm able to access them in my env and there is no official documentation about these

I guess these are from plugin named : Sort Utilities, if you are not able to access them means you don't have the plug-in in your env.
to access you have to add the plugin in your env

Apologies. they were part of a plugin .

I think you have a misprint in here. You have a rule input for "ascending" as i'd expect, but instead of using that you have "or(ri!array)".

I would expect perhaps that part to say "ascending: a!defaultValue(ri!ascending, true())" - and just note that the default behavior of the expression rule will be to sort in an ascending manner unless specified otherwise.

I think a plugin is overkill for this kind of functionality. Probably best to use the method suggested by Harshit.

Yeah, that's gotta be a typo.

Good catch, Mike Schmitt 
Fixed!!