This is an example of the Zip (applicative functor) experimental extension to Computation Expression. using for .. and ... do, sources are merges using the .Merge(xs,f) method. If Select is defined and the rest of the expression is a simple projections, the result is Select(Merge(xs,ys), projection) else it is Bind(Merge(xs,ys), rest of the expr…

Zip computation

open System

type ZipBuilder() =
    member t.Zip(xs,ys) = List.zip xs ys
    member t.For(xs,f) = List.collect f xs
    member t.Yield x = [x]
    member t.Select(xs,f) =
       List.map f xs
    member t.Zero() = []

let zip = new ZipBuilder()


let xs = [ 1; 2; 7]
let ys = [ 4; 6; 9]
let zs = [ 2; 4; 6]
//let r = 
zip {
    for x in xs
    and y in ys
    and z in zs do
    yield x + y + z
} |> List.iter (printfn "%d")
// the result is [ 7; 12; 22]