How to Select by LINQ into anonymous type in F#

Question

I have this code snippet, which creates an array of anonymously typed elements with properties Name and FirstLetter:

string[] arr = { "Dennis", "Leo", "Paul" };

var myRes = arr.Select(a => new { Name = a, FirstLetter = a[0] });

I would like to do the same in F#. I tried:

let names = [| "Dennis"; "Leo"; "Paul" |]

let myRes = names.Select(fun a -> {Name = a; FirstLetter = a[0]} )

But this doesn't compile. It says:

The record label 'Name' is not defined.

How can I get this line to work in F#?

Answer 1

As in comments, F# doesn't support anonymous type. So if you want to project your sequence into another sequence, create a record, which is essentially a tuple with named fields.

type p = { 
  Name:string;
  FirstLetter: char 
}

let names = [| "Dennis"; "Leo"; "Paul" |]
let myRes = names.Select(fun a -> {Name = a; FirstLetter = a.[0]} )