Pattern matching on the beginning of a string in f#

Question

I am trying to match the beginning of strings in f#. Not sure if I have to treat them as a list of characters or what. Any suggestions would be appreciated.

Here is a psuedo code version of what I am trying to do

let text = "The brown fox.."  match text with | "The"::_ -> true | "If"::_ -> true | _ -> false 

So, I want to look at the beginning of the string and match. Note I am not matching on a list of strings just wrote the above as an idea of the essence of what I am trying to do.

Answer 1

Parameterized active patterns to the rescue!

let (|Prefix|_|) (p:string) (s:string) =     if s.StartsWith(p) then         Some(s.Substring(p.Length))     else         None  match "Hello world" with | Prefix "The" rest -> printfn "Started with 'The', rest is %s" rest | Prefix "Hello" rest -> printfn "Started with 'Hello', rest is %s" rest | _ -> printfn "neither"