Question

Soo… F# no longer has IEnumerable.map_with_type… which is the way people were mapping over collections. How do I do that now?

let urlPat = 'href\\s*=\\s*(?:(?:\\\'(?<url>[^\\\']*)\\\')|(?<url>[^\\s]* ))';; let urlRegex = new Regex(urlPat) let matches =      urlRegex.Matches(http('http://www.google.com'))  let matchToUrl (urlMatch : Match) = urlMatch.Value let urls = List.map matchToUrl matches 

Thanks!

Answer 1

you would write the last line like this:

let urls = Seq.map matchToUrl (Seq.cast matches);; 

And this can be written in a nicer way using pipelining operator:

let urls = matches|> Seq.cast |> Seq.map matchToUrl;; 

F# automatically figures out what is the right target type (because it knows what matchToUrl looks like). This is available only for Seq, so you can use List.of_seq to get the data into a list again.