Active Patterns

[gusty]

At the moment we have only one active recognizer: Parse and I'm not very happy with the name as it does exactly the opposite (maybe Parsed is a better name, or ToString or String given that's the inverse function).

But the goal of this issue is to compile a list of useful active patterns and discuss if it worth having them in F#+.

Here are some:

• IgnoreCase for case insensitive string comparison
• Date (y, m, d) to deconstruct a DateTime to date components. It could be overloaded to handle tuples.
• Null check

(I might add more stuff to this list)

[wallymathieu]

Parsed sounds a bit weird at first, though better than Parse. Example code reads better:

let ipAndPort : (System.Net.IPAddress * int) option = 
    match "192.168.0.1:8001".Split ':' with 
    | [|Parsed ip; Parsed port|] -> Some (ip, port)
    | _ -> None

Ignore case could be useful:

module CustomerId=
  let tryParse CustomerId option = 
    match "c_24577".Split '_' with 
    | [|IgnoreCase "C"; Parsed id|] -> Some (CustomerId id)
    | _ -> None