appending results to array after parallel processing

Question

Some eloquency questions:

A. How to add a list that was formed from parallel processing directly to the a Concurrent results array in an eloquent way.

let results = System.Collections.Concurrent.ConcurrentBag<string>()
let tasks = System.Collections.Generic.List<string>()
tasks.add("a")
tasks.add("b")
let answers = tasks
 |> Seq.map asyncRequest
 |> Async.Parallel
 |> Async.RunSynchronously
 |> Array.toList
Array.append results answers

Attempt Is there a way to append via pipe operator?

let answers = tasks
 |> Seq.map asyncRequest
 |> Async.Parallel
 |> Async.RunSynchronously
 |> Array.append results

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B. Is there a way to add items via List constructor?

let tasks = System.Collections.Generic.List<string>()
tasks.add("a")
tasks.add("b")

---

C. Is there a way to construct a queue from array using Queue constructor?

let items: string[] = [|"a", "b", "c"|]
let jobs = System.Collections.Generic.Queue<string>()
items |> Array.map jobs.Enqueue |> ignore

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Answer 1

A. you can't use Array.append on results, because results is a ConcurrentBag, but Array.append expects its argument to be an Array. To add stuff to ConcurrentBag, use its Add method. Add items one by one:

tasks
 |> Seq.map asyncRequest
 |> Async.Parallel
 |> Async.RunSynchronously
 |> Array.iter results.Add

Adding items one by one is a little inefficient. If your ConcurrentBag is really created right in the same function, as your example shows, you may consider using its constructor that takes an IEnumerable<T>:

let answers = tasks
 |> Seq.map asyncRequest
 |> Async.Parallel
 |> Async.RunSynchronously
let results = System.Collections.Concurrent.ConcurrentBag<string>( answers )

B. yes, there is a way to add stuff to a System.Collections.Generic.List<T>. This class provides a handy Add method for this purpose:

tasks.Add "a"
tasks.Add "b"

Enclosing the argument in parentheses (as in your attempt) is not necessary, but allowed:

tasks.Add("a")
tasks.Add("b")

C. yes, there is a way to construct a queue from an array. The Queue class has a constructor that takes an IEnumerable<T>, and arrays implement IEnumerable<T>, so you can call that constructor on an array:

let jobs = System.Collections.Generic.Queue<string>( items )

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Please note that you hardly needed my help to get any of the above information. Everything is freely available on MSDN (see links above) or from autocompletion/intellisense in your favorite code editor.