F#: How do i split up a sequence into a sequence of sequences

Question

Background:

I have a sequence of contiguous, time-stamped data. The data-sequence has gaps in it where the data is not contiguous. I want create a

Answer 1

You seem to want a function that has signature

(`a -> bool) -> seq<'a> -> seq>

I.e. a function and a sequence, then break up the input sequence into a sequence of sequences based on the result of the function.

Caching the values into a collection that implements IEnumerable would likely be simplest (albeit not exactly purist, but avoiding iterating the input multiple times. It will lose much of the laziness of the input):

let groupBy (fun: 'a -> bool) (input: seq) =
  seq {
    let cache = ref (new System.Collections.Generic.List())
    for e in input do
      (!cache).Add(e)
      if not (fun e) then
        yield !cache
        cache := new System.Collections.Generic.List()
    if cache.Length > 0 then
     yield !cache
  }

An alternative implementation could pass cache collection (as seq<'a>) to the function so it can see multiple elements to chose the break points.