My Regex Lessons (Probably 1 of many…)

OK, that previous post had a couple of minor problems.

First that regular expression – terribly unwieldy. I haven’t managed to shorten it fully yet, but this is marginally better:

"([\w\s:;… add whatever characters are valid here…]*)(?:\",|\"$)

Secondly, I wasn’t fully thinking through the matches/groups/captures hierarchy. I kept getting empty captures being reported back without understanding why I was getting them.

Updated code here:

open System
open System.Text.RegularExpressions

let (|ActiveRegex|_|) regex str =
   let ms = Regex(regex).Matches(str)
   if ms.Count > 0
   then Some ((Seq.cast ms : Match seq))
   else None

let matches s re =
    match s with
    | ActiveRegex re results -> results
    | _ -> Seq.empty

let capturesSeq s p =
    seq{
        for m in matches s p ->
            Seq.skip 1 (seq{for g in m.Groups -> g.Value})
        }
    |> Seq.concat

let csvRegex = "\"([\w\s:;~!@#$%\^&\*_<>,\.\\\/\|\[\]\{\}\(\)\-\+\?]*)(?:\",|\"$)"

let testLine = "\"31\",\"a 1\",\"b-2\",\"c+3\",\",.;~!@#$%^&*()\/?><,.|{}[]_+-\",\"\",\"14/05/2010 12:12:20 a.m.\",\"1: 2; 3. 4? 5[ 6] 7& 8*\",\"a,b\""

capturesSeq testLine csvRegex
|> Seq.iter (fun x -> printfn "%A" x)