Given a mapping program where I map from an array of strings to a discriminated union, I want to select an instance of a particular DU type. I know that there will be 0 or 1 instances. Is there a smarter way to do it than this?
type thing = { One:int; Two:int; Three:int}
type data =
| Alpha of int
| Bravo of thing
| Charlie of string
| Delta of Object
//generate some data
let listData = [
Alpha(1);
Alpha(2);
Bravo( { One = 1; Two = 2; Three = 3 } );
Charlie("hello");
Delta("hello again")]
//find the 0 or 1 instances of bravo and return the data as a thing
let result = listData
|开发者_如何学运维> List.map( function | Bravo b -> Some(b) | _ -> None)
|> List.filter( fun op -> op.IsSome)
|> (function | [] -> None | h::t -> Some(h.Value))
Thanks
How about
let result =
listData
|> List.tryPick (function | Bravo b -> Some b | _ -> None)
List.tryFind will do the trick:
let result = listData
|> List.tryFind (function | Bravo b -> true | _ -> false)
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