What is the most idiomatic style to force a computation using Sequences in f#?

Question

I have a side-effective operation

     securities |> Seq.map (fun x -> request.Append("securities",x))

What is the most idiomatic way to have the code perform ?

I wrote a Seq.Doit, but it itches

  module Seq =
     let Doit sa = sa |> Seq.toArray |> ignore

Answer 1

Deferred sequences are used when you create sequences using Seq.delay or sequence expression seq{}. Any function on sequence returning any datatype other than seq can force computation.

Alternatively, you can use for loop instead of Seq.iter:

for s in securities do
   request.Append("securities", s)

If you want to hide side effects and return request for later use, Seq.fold is a good choice:

securities |> Seq.fold (fun acc x -> acc.Append("securities", x); acc) request

Answer 2

I think Seq.iter is appropriate in this case. From the MSDN reference page:

Seq.iter : ('T -> unit) -> seq<'T> -> unit

Applies the given function to each element of the collection.

So, supposing that request.Append does not return anything, your code becomes:

securities |> Seq.iter (fun x -> request.Append("securities", x))