How do I concatenate a list of strings in F#?

jacko_12948 0
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I'm trying this at the moment, but I haven't quite got the method signature worked out... anyone? messages is a field of seq[string]

let messageString = List.reduce(messages, fun (m1, m2) -> m1 + m2 + Environment.NewLine)
f#
5 Answers

just one more comment,

when you are doing with string, you'd better use standard string functions.

The following code is for EulerProject problem 40. 

let problem40 =
    let str = {1..1000000} |> Seq.map string |> String.concat ""
    let l = [str.[0];str.[9];str.[99];str.[999];str.[9999];str.[99999];str.[999999];]
    l |> List.map (fun x-> (int x) - (int '0')) |> List.fold (*) 1

if the second line of above program uses fold instead of concat, it would be extremely slow because each iteration of fold creates a new long string.

user_1838280
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