Home/ Questions/Q 8906671
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-15T02:42:59+00:00

I have a Dictionary over which I initially iterated thusly: myDictionary |> Seq.iter (fun

  • 0

I have a Dictionary over which I initially iterated thusly:

myDictionary |> Seq.iter (fun kvp -> doSomething kvp.Key kvp.Value)

Later, I discovered that I could make use of the KeyValue active pattern, and do this:

myDictionary |> Seq.iter (fun (KeyValue (k, v)) -> doSomething k v)

Knowing that active patterns aren’t some form of preprocessor directive, how am I able to substitute the kvp argument in the lambda for a function that decomposes it?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Functions arguments call always be destructured using pattern matching. For instance:

    let getSingleton = fun [x] -> x
let getFirst = fun (a,b) -> a
let failIfNotOne = fun 1 -> ()
let failIfNeitherOne = fun (x,1 | 1,x) -> ()

    Semantically, fun<pat>-><body> is roughly equivalent to

    fun x ->
    match x with
    |<pat>-><body>

    | _ -> raise MatchFailureException(...)

    • 0