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Active pattern example

Example active pattern for tweet.

Active pattern

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/// Checks to see if a list has exactly one element
/// and checks to see if that one element is a
/// particular given element.
let (|Singleton|_|) element listarg =
  match listarg with
  | [x]
    -> if x = element
        then Some ()
        else None
  | _ -> None
val element : 'a (requires equality)
val listarg : 'a list (requires equality)
val x : 'a (requires equality)
union case Option.Some: Value: 'T -> Option<'T>
union case Option.None: Option<'T>
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More information

Link:http://fssnip.net/lE
Posted:5 years ago
Author:Robert Nielsen
Tags: active pattern , twitter , example